avalaris - Services - Backup

ADR
Advanced Digital Recording (ADR) is a magnetic tape data storage format developed by OnStream from 1998 to 2003. Since the demise of OnStream, the format has been orphaned. ADR is an 8-track, linear tape format.
AIT
AIT (advanced intelligent tape) is a magnetic tape and drive system used for computer data storage and archiving. The tapes measure eight millimeters (8 mm) across. A helical scanning technique, similar to that used in Mammoth drives, optimizes the data transfer rate and the storage capacity. Some AIT cartridges can hold up to 65 gigabytes (GB) of data when compression is used. The algorithm is known as adaptive lossless data compression (ALDC). The maximum extent of compression is 2.1:1. An AIT drive can transfer data at speeds of up 7.8 Mbps with compression. AIT is one of several high-volume, high-speed tape drive technologies. Competing devices include the linear tape open (LTO) drive, the Mammoth drive, and the digital linear tape (DLT) drive
AME
AME (Advanced Metal Evaporated) Tape: Patented process for depositing a pure metal magnetic layer directly on the base film without adhesive or binders. The benefit from this AME technology is maximum recording performance. Often used with AIT-tapes.
AOD - Advanced Optical Disc
Blu-ray’s competing HD-DVD technology format. AOD and Blu-ray are similar in that they both use 405nm-wavelength blue-violet laser technology, in contrast to the 650nm-wavelength red laser technology used in traditional DVD formats. However, while Blu-ray has a storage capacity of 27GB on a single-layer disc, AOD has a storage capacity of 20GB on a single-layer disc. AOD was developed jointly by Toshiba and NEC.
Arbitrated Loop (FC AL)
Arbitrated loop, also known as FC-AL, is a Fibre Channel topology in which devices are connected in a one-way loop fashion in a ring topology. Historically it was a lower-cost alternative to a fabric topology. It allowed connection of many servers and computer storage devices without using then very costly Fibre Channel switches. As of 2007 the cost of the switches dropped considerably, so FC-AL is rarely used for a server-to-storage communication. It is however still commonly utilized on backend of some disk array controllers.
Array
Two or more hard-drives which appear as one single drive in the network.
Array-Controller active-active
Several external RAID-controllers which independently allow access to data.
Array-Controller active-passive
External array-controller that stays in waiting-position during error-free data-access. It replaces the defective array-controller in case of a system-error.
ASPI
ASPI, the Advanced SCSI Programming Interface provides an API originated by Adaptec which standardises communication on a computer bus between a SCSI host adapter on the one hand and SCSI (and ATAPI) peripherals on the other.
Autoloader
An autoloader, or autochanger, is a data storage device consisting of at least one tape drive (the drive), a method of loading tapes into the drive (the robot), and a storage area for tapes (the magazine). Larger autoloaders with multiple drives, robots, and magazines are known as tape libraries. Other types of autoloaders may operate with floppy disks and compact disks.
Backup
Backup is the activity of copying files or databases so that they will be preserved in case of equipment failure or other catastrophe. Backup is usually a routine part of the operation of large businesses with mainframes as well as the administrators of smaller business computers. For personal computer users, backup is also necessary but often neglected. The retrieval of files you backed up is called restoring them.
Backup, differential
A cumulative backup of all changes made after the last full backup. The advantage to this is the quicker recovery time, requiring only a full backup and the latest differential backup to restore the system. The disadvantage is that for each day elapsed since the last full backup, more data needs to be backed up, especially if a majority of the data has been changed.
Backup, incremental
A normal incremental backup will only back up files that have been changed since the last backup of any type. This provides the quickest means of backup, since it only makes copies of files that have not yet been backed up. For instance, following a full backup on Friday, Monday’s tape will contain only those files changed since Friday. Tuesday’s tape contains only those files changed since Monday, and so on. The downside to this is that in order to perform a full restore, one needs to restore the last full backup first, followed by each of the subsequent incremental backups to the present day in the correct order. Should any one of these backup copies be damaged (particularly the full backup), the restore will be incomplete.
Backup, selective
The administrator decides which data, files, directories or partitions should be saved.
Backup, full
The full backup stores all files and folders, frequent full backups result in faster and simpler restore operations. Remember that when you choose other backup types, restore jobs may take longer. It would be ideal to make full backups all the time, because they are the most comprehensive and are self-contained. However, the amount of time it takes to run full backups often prevents us from using this backup type. Full backups are often restricted to a weekly or monthly schedule, although the increasing speed and capacity of backup media is making overnight full backups a more realistic proposition.
Backup-Server
A computer and storage-system, that functions as network device and provides services for securing and recovering data.
Blade Server
Blade servers are self-contained computer servers, designed for high density. Whereas a standard rack-mount server can exist with (at least) a power cord and network cable, blade servers have many components removed for space, power and other considerations while still having all the functional components to be considered a computer. A blade enclosure, which can hold multiple blade servers, provides services such as power, cooling, networking, various interconnects and management—though different blade providers have differing principles around what should and should not be included in the blade itself (and sometimes in the enclosure altogether). Together these form the blade system. In a standard server-rack configuration, 1U (one rack unit, 19" wide and 1.75" tall) is the minimum possible size of any equipment. The principal benefit of, and the reason behind the push towards, blade computing is that components are no longer restricted to these minimum size requirements. The most common computer rack form-factor being 42U high, this limits the number of discrete computer devices directly mounted in a rack to 42 components. Blades do not have this limitation; densities of up to 84 discrete servers per rack are achievable with the current generation of blade systems.
Bluefin + SAN-Management
Cooperation of components within a heterogenous Storage Area Network (SAN) today is nearly completely guaranteed. However producers face the challenge to unify the administration of network nodes, data and access authorizations as well as the surveillance and security of data transfer - independent of hardware, operating systems and applications. As within LANs there was no demand for administration of storage devices, the backlog for SANs is high. A complete strategy for this problem is the "Bluefin"-specification of SNIA. Bluefin defines a general gateway for administration of storage-nets. It ought to identify and classify objects according to consistent criteria. Real and virtual resources in the company can be monitored as well and be transmitted by using a shared transport-mechanism. Bluefin therewith is the project name for far more than an API (Application Programming Interface).
Blue-ray
Bluray Disc (also known as Bluray or BD) is an optical disc storage media format. Its main uses are high-definition video and data storage. The disc has the same dimensions as a standard DVD or CD. The name Blu-ray Disc is derived from the blue laser (violet coloured) used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A dual layer Blu-ray Disc can store 50 GB, almost six times the capacity of a dual layer DVD. Blu-ray Disc was developed by the Blu-ray Disc Association, a group of companies representing consumer electronics, computer hardware, and motion picture production. As of July 2, 2008 more than 650 Blu-ray Disc films have been commercially released in the United States and more than 410 Blu-ray Disc titles have been released in Japan. During the high definition optical disc format war, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba — the main company supporting HD DVD — announced it would no longer develop, manufacture and market HD DVD players and recorders, leading almost all other HD DVD supporters to follow suit, effectively ending the format war.
Cache
A cache is a temporary storage area where frequently accessed data can be stored for rapid access. Once the data is stored in the cache, future use can be made by accessing the cached copy rather than re-fetching or recomputing the original data, so that the average access time is shorter.
DAT
Digital Audio Tape (DAT or R-DAT) is a signal recording and playback medium developed by Sony in the mid 1980s. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As the name suggests the recording is digital rather than analog. DAT has the ability to record at higher, equal or lower sampling rates than a CD (48, 44.1 or 32 kHz sampling rate respectively) at 16 bits quantization. If a digital source is copied then the DAT will produce an exact clone, unlike other digital media such as Digital Compact Cassette or non-Hi-MD MiniDisc, both of which use lossy data compression. Like most formats of videocassette, a DAT cassette may only be recorded on one side, unlike an analog compact audio cassette.
Data Reliability
Data Reliability refers to the mean time to data loss (MTDL).
Data Transfer Rate
Data transfer rate or just transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. Transfer rates can serve several functions. The response time can help a network administrator pinpoint where slowdowns and potential hangups exist in a network. By analyzing data transfer rates and adjusting accordingly as a preventative measure, a system can be made more efficient and will be more prepared to handle extra bandwidth constraints in times of heavy usage.
Data compression
Data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. One popular instance of compression with which many computer users are familiar is the ZIP file format, which, as well as providing compression, acts as an archiver, storing many source files in a single destination output file. As with any communication, compressed data communication only works when both the sender and receiver of the information understand the encoding scheme. For example, this text makes sense only if the receiver understands that it is intended to be interpreted as characters representing the English language. Similarly, compressed data can only be understood if the decoding method is known by the receiver. Compression is useful because it helps reduce the consumption of expensive resources, such as hard disc space or transmission bandwidth (computing). On the downside, compressed data must be decompressed to be used, and this extra processing may be detrimental to some applications. For instance, a compression scheme for video may require expensive hardware for the video to be decompressed fast enough to be viewed as it's being decompressed (the option of decompressing the video in full before watching it may be inconvenient, and requires storage space for the decompressed video). The design of data compression schemes therefore involves trade-offs among various factors, including the degree of compression, the amount of distortion introduced (if using a lossy compression scheme), and the computational resources required to compress and uncompress the data.
Data Security
Manyfold protection of data is an important issue, as there are just as many ways of misuse or unauthorised access through third parties. In a first step data is defined through assigned access rights to prevent unauthorized access. Encryption ensures that data is not available to anybody in it's readable state. Manipulation of information as by viruses is prevented through acknowledging and warding off of attacks by security programs. Yet - a data security of 100 % is still not possible with today's known measures.
Data Backup
Backup refers to making copies of data so that these additional copies may be used to restore the original after a data loss event. These additional copies are typically called "backups." Backups are useful primarily for two purposes. The first is to restore a state following a disaster (called disaster recovery). The second is to restore small numbers of files after they have been accidentally deleted or corrupted. Backups are typically that last line of defense against data loss, and consequently the least granular and the least convenient to use.
DDS
Digital Data Storage (DDS) is a format for storing and backing up computer data on magnetic tape that evolved from Digital Audio Tape (DAT) technology, which was originally created for CD-quality audio recording. In 1989, Sony and Hewlett Packard defined the DDS format for data storage using DAT tape cartridges. Tapes conforming to the initial DDS format can be read by either DAT or DDS tape machines. However, most DDS tape drives cannot retrieve the audio stored on a DAT cartridge. DDS uses 3.8 millimeter wide tape. Initially, the tape was 60 or 90 meters long, although advancements in materials technology have allowed the length to be increased significantly in successive versions. A DDS tape drive uses helical scanning for recording, the same process used by a video cassette recorder (VCR). There are two read heads and two write heads. The read heads verify the data that has been written (recorded). If errors are present, the write heads rewrite the data. A DDS cartridge needs to be retired after 2,000 passes or 100 full backups.
DFS
Distributed File System, or DFS, is a set of client and server services that allow a large enterprise to organize many distributed SMB file shares into a distributed file system. DFS provides location transparency and redundancy to improve data availability in the face of failure or heavy load by allowing shares in multiple different locations to be logically grouped under one folder, or DFS root.
Direct Access Storage Device (DASD)
In mainframe computers and some minicomputers, a direct access storage device, or DASD, is any secondary storage device which has relatively low access time for all its capacity.
Directors
Typically a director is used in the Backbone of large corporation-wide SANs. It is a high availability Fabric Switch, which is characterised by it's high switching-bandwiths and a high port-density. Significant specifications of directors are the fully redundant, hot swap exchangeable components and internal failover-mechanisms. A SAN constructed with directors reaches because of these specifications an availability of up to 99,999 %, which corresponds with a downtime of less than 5 minutes per year. Typically, server and storage-components are connected each through two ports on different port-cards to the director, so that communication is not disrupted even when one port fails.
Disaster Protection
Measures that can provoke an unforseeable downtime of a computer or server.
DLT (Digital Linar Tape)
DLT uses linear serpentine recording with multiple tracks on half-inch (12.7 mm) wide tape. The cartridges contain a single reel and the tape is pulled out of the cartridge by means of a leader tape attached to the takeup reel inside the drive. The drive leader tape is buckled to the cartridge leader during the load process. Tape speed and tension are controlled electronically via the reel motors; there is no capstan. The tape is guided by 4 to 6 rollers that touch only the back side of the tape. Tape material is metal particle tape (MP/AMP.) SDLT adds an optical servo system that reads servo patterns on the back of the tape, in order to keep the data tracks on the front of the tape correctly aligned with the read/write heads. This is important for newer tape media, which have very thin dense data tracks; 256, 384 and 768 data tracks on a half inch wide tape are now common. DLT7000 and 8000 tilt the head forward and backward to reduce crosstalk between adjacent tracks through azimuth; this is called Symmetric Phase Recording. All (S)DLT drives support hardware data compression. The often-used compression factor of 2:1 is optimistic and generally only achievable for text data; a more realistic factor across a file system is 1.3:1 to 1.5:1. Note that drive compression applied to pre-compressed data can actually make the written data larger than having compression turned off in the tape drive. Media are guaranteed for 30 years of data retention under specified environmental conditions; however, they are easily damaged by mishandling (dropping or improper packaging during shipment.)
DMA
Direct memory access (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. Many hardware systems use DMA including disk drive controllers, graphics cards, network cards, sound cards and GPUs. DMA is also used for intra-chip data transfer in multi-core processors, especially in multiprocessor system-on-chips, where its processing element is equipped with a local memory (often called scratchpad memory) and DMA is used for transferring data between the local memory and the main memory. Computers that have DMA channels can transfer data to and from devices with much less CPU overhead than computers without a DMA channel. Similarly a processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time, overlapping computation and data transfer.
E-IDE
Enhanced (sometimes "Expanded") IDE is a standard electronic interface between your computer and its mass storage drives. EIDE's enhancements to Integrated Drive Electronics (IDE) make it possible to address a hard disc larger than 528 Mbytes. EIDE also provides faster access to the hard drive, support for Direct Memory Access (DMA), and support for additional drives, including CD-ROM and tape devices through the AT Attachment Packet Interface.
Exabyte, EByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
External Array-Controller
RAID-Controller located in an external RAID-casing.
Fabric Switch
Switched fabric, switching fabric, or just fabric, is a network topology where network nodes connect with each other via one or more network switches (particularly via crossbar switches, hence the name). The term is popular in telecommunication, Fibre Channel storage area networks and other high-speed networks, including InfiniBand.
Failed Drive Mode
Restricted Performance-mode, after a defective hard disc went to Array.
Failover
Failover is the capability to switch over automatically to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the reviously active server, system, or network. Failover happens without human intervention and generally without warning, unlike switchover.
Fibre Channel
Fibre Channel is a technology designed for very high performance low-latency data transfer among various types of devices, as defined by a family of ANSI standards developed by INCITS T11. Data rates of 100, 200, 400, and 1200M-bytes/sec are defined for fiber optic links up to 50 km and for copper links. The links are full duplex, providing total bandwidth double the link rate. Topologies include point-to-point, shared loop, and switched. Fibre Channel is mapped to several protocol layers, the most popular ones being the storage protocols SCSI (FCP) and ESCON (FICON). Fibre Channel is the principal technology used to implement Storage Area Networks (SANs).
FICON
FICON (Fiber Connectivity) is the IBM proprietary name for the ANSI FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre Channel (FC) protocol. It is a FC layer 4 protocol used to map both IBM’s antecedent (either ESCON or parallel) channel-to-control-unit cabling infrastructure and protocol onto standard FC services and infrastructure. The topology is fabric utilizing FC switches or directors. Valid rates include 1, 2, and 4 Gigabit data rates at distances up to 100 km.
GigaByte, GByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
Helical Scan
Helical scan is a method of recording high bandwidth signals onto magnetic tape. It is used in video tape recorders, video cassette recorders, digital audio tape recorders, and some computer tape drives. In a fixed head system, tape is drawn past the head at a constant speed. The head creates a fluctuating magnetic field in response to the signal to be recorded, and the magnetic particles on the tape are forced to line up with the field at the head. As the tape moves away, the magnetic particles carry an imprint of the signal in their magnetic orientation. If the tape moves too slowly, a high frequency signal will not be imprinted — the particles' polarity will simply oscillate in the vicinity of the head, to be left in a random position. Thus the bandwidth capacity of the recorded signal can be seen to be related to tape speed — the faster the speed, the higher the frequency that can be recorded. Video and digital audio need considerably more bandwidth than analogue audio, so much so that tape would have to be drawn past the heads at very high speed in order to capture this signal. Clearly this is impractical, since tapes of immense length would be required. (However, see VERA for details of a partially-successful linear videotape system.) The generally adopted solution is to rotate the head against the tape at high speed, so that the relative velocity is high, but the tape itself moves at a slow speed. To accomplish this, the head must be tilted so that at each rotation of the head, a new area of tape is brought into play; each segment of the signal is recorded as a diagonal stripe across the tape. This is known as a helical scan because the tape wraps around the circular drum at an angle, travelling up like a helix.
Hot Spare
A hot spare or hot standby is used as a failover mechanism to provide reliability in system configurations. The hot spare is active and connected as part of a working system. When a key component fails, the hot spare is switched into operation. More generally, a hot standby can be used to refer to any device or system that is held in readiness to overcome an otherwise significant start-up delay.
Hot Swap
Hot swapping and hot plugging are terms used to separately describe the functions of replacing system components; hot swapping describes changing components like fans and power supplies which do not interact with the system software, while hot plugging describes changing or adding components like hard drives which do interact with the operating system.
HSM
Hierarchical Storage Management (HSM) is a data storage technique which automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as hard disc drive arrays, are more expensive (per byte stored) than slower devices, such as optical discs and magnetic tape drives. While it would be ideal to have all data available on high-speed devices all the time, this is prohibitively expensive for many organizations. Instead, HSM systems store the bulk of the enterprise's data on slower devices, and then copy data to faster disk drives when needed. In effect, HSM turns the fast disk drives into caches for the slower mass storage devices. The HSM system monitors the way data is used and makes best guesses as to which data can safely be moved to slower devices and which data should stay on the fast devices.
INCITS
The International Committee for Information Technology Standards, or INCITS is an ANSI-accredited forum of IT developers. It was formerly known as the X3 and NCITS. INCITS coordinates technical standards activity between ANSI in the USA and joint ISO/IEC committees worldwide. This provides a mechanism to create standards that will be implemented in many nations.
InfiniBand
InfiniBand is a switched fabric communications link primarily used in high-performance computing. Its features include quality of service and failover, and it is designed to be scalable. The InfiniBand architecture specification defines a connection between processor nodes and high performance I/O nodes such as storage devices. It is a superset of the Virtual Interface Architecture. Like Fibre Channel, PCI Express, Serial ATA, and many other modern interconnects, InfiniBand is a point-to-point bidirectional serial link intended for the connection of processors with high speed peripherals such as disks. It supports several signalling rates and, as with PCI Express, links can be bonded together for additional bandwidth.
Information Lifecycle Management (ILM)
Information Lifecycle Management refers to a wide-ranging set of strategies for administering storagesystems on computing devices. Specifically, four categories of storage strategies may be considered under the auspices of ILM. Information Lifecycle Management (sometimes abbreviated ILM) is the practice of applying certain policies to the effective management of information throughout its useful life. This practice has been used by Records and Information Management (RIM) Professionals for over three decades and had its basis in the management of information in paper or other physical forms (microfilm, negatives, photographs, audio or video recordings and other assets). ILM includes every phase of a "record" from its beginning to its end. And while it is generally applied to information that rises to the classic definition of a record (Records management), it applies to any and all informational assets. During its existence, information can become a record by being identified as documenting a business transaction or as satisfying a business need. In this sense ILM has been part of the overall approach of ECM Enterprise content management. However, in a more general perspective the term "business" must be taken in a broad sense, and not forcibly tied to direct commercial or enterprise contexts. While most records are thought of as having a relationship to enterprise business, not all do. Much recorded information serves to document an event or a critical point in history. Examples of these are birth, death, medical/health and educational records. e-Science, for example, is an emerging area where ILM has become relevant.
Interface
An interface defines the communication boundary between two entities, such as a piece of software, a hardware device, or a user. It generally refers to an abstraction that an entity provides of itself to the outside. This separates the methods of external communication from internal operation, and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide multiple abstractions of itself. It may also provide a means of translation between entities which do not speak the same language, such as between a human and a computer. Because interfaces are a form of indirection, some additional overhead is incurred versus direct communication.
Interrupt
An interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change in execution. A hardware interrupt causes the processor to save its state of execution via a context switch, and begin execution of an interrupt handler. Software interrupts are usually implemented as instructions in the instruction set, which cause a context switch to an interrupt handler similar to a hardware interrupt. Interrupts are a commonly used technique for computer multitasking, especially in real-time computing. Such a system is said to be interrupt-driven.
IRQ (Interrupt Request)
Interrupt request (or IRQ) is used to refer to either the act of interrupting the bus lines used to signal an interrupt, or the interrupt input lines on a Programmable Interrupt Controller (PIC). Interrupt lines are often identified by an index with the format of IRQ followed by a number. For example, on the Intel 8259 family of PICs there are eight interrupt inputs commonly referred to as IRQ0 through IRQ7. In x86 based computer systems that use two of these PICs, the combined set of lines are referred to as IRQ0 through IRQ15. Technically these lines are named IR0 through IR7, and the lines on the ISA bus to which they were historically attached are named IRQ0 through IRQ15. Newer x86 systems integrate an Advanced Programmable Interrupt Controller (APIC) that conforms to the Intel APIC Architecture. These APICs support a programming interface for up to 255 physical hardware IRQ lines per APIC, with a typical system implementing support for only around 24 total hardware lines.
ISA
Integrated System Architecture is a bus-system established by IBM in 1981 for the use on PCs. The bus-system regulates the dataflow between processor and boards and interfaces. The ISA-bus works with a maximum of 8 MHz clock rate. It is available with 8-bit and 16-bit transmission speed.
iSCSI
iSCSI (for "Internet SCSI") protocol allows clients (called initiators) to send SCSI commands (CDBs) to SCSI storage devices (targets) on remote servers. It is a popular Storage Area Network (SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts (such as database and web servers) with the illusion of locally-attached disks. Unlike Fibre Channel, which requires special-purpose cabling, iSCSI can be run over long distances using existing network infrastructure. iSCSI uses TCP/IP (typically TCP ports 860 and 3260). In essence, iSCSI simply allows two hosts to negotiate and then exchange SCSI commands using IP networks. By doing this, iSCSI takes a popular high-performance local storage bus and emulates it over wide-area networks, creating a storage area network (SAN). Unlike some SAN protocols, iSCSI requires no dedicated cabling; it can be run over existing switching and IP infrastructure. As a result, iSCSI is often seen as a low-cost alternative to Fibre Channel, which requires dedicated infrastructure. Although iSCSI can communicate with arbitrary types of SCSI devices, system administrators almost always use it to allow server computers (such as database servers) to access disk volumes on storage arrays.
JBOD
JBOD stands for Just a Bunch of Disks. The controller treats each drive as a stand-alone disk, therefore each drive is an independent logical drive. JBOD does not provide data redundancy.
KiloByte, KByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
LTO
Linear Tape-Open (or LTO) is a magnetic tape data storage technology developed as an open alternative to the proprietary Digital Linear Tape (DLT). The technology was developed and initiated by Seagate, Hewlett-Packard, and IBM. The standard form-factor of LTO technology goes by the name "Ultrium".
Magnetic tape
Magnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany, based on the concept of magnetic wire recording. Devices that record and playback audio and video using magnetic tape are generally called tape recorders and video tape recorders respectively. A device that stores computer data on magnetic tape can be called a tape drive, a tape unit, or a streamer.
Mammoth
This tape recording technology was developed by Exabyte and uses -mm-tapes. Capacities range from 20 (uncompressed) to 40 GByte (compressed). Data transfer rates lie between 3 and 6 MByte per second.
Mammoth-2 (M2)
Second generation Mammoth-streamers possess an uncompressed capacity of 60 GByte and compressed more than 150 GByte. Data transfer rates lie between 43 (uncompressed) and 100 GByte per hour.
MegaByte, MByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
MIC
Storeage media with Memory In Cassette (MIC) possess an integrated memory chip (EEPROM). With it volume, partition, data specification and error-count of data on the storage media can be fetched. This should enable faster navigation on the tape. Sony makes use of this kind of partitioning on the tape of it's AIT-technology.
Mirroring
Mirroring (RAID 1) of the complete content of a drive.
MLR
Multi-Channel-Linear-Technology (MLR) was developed by Tandberg Data as successor of the SLR-technology. MLR is an edvancement of QIC-format. Corresponding streamers possess four writing- and eight reading-heads. Writing-processes can be executed simultaneously. The first media-generation provides an uncompressed storage capacity of 16 GByte. SLR-50-drives reach a net capacity of 50 GByte.
MTDA
Mean time between data access
MTDL
Mean time between data loss
Multitasking
Parallel processing of several application programs
Multithreading
Multithreading computers have hardware support to efficiently execute multiple threads. These are distinguished from multiprocessing systems (such as multi-core systems) in that the threads must all operate in the same address space, as there is only one shared set of CPU caches and one translation lookaside buffer (TLB). As a result, multithreading can only take advantage of parallelism of within a program, whereas multiprocessing systems can run multiple programs in parallel. Where multiprocessing systems include multiple complete processing units, multithreading aims to increase utilization of a single core by leveraging thread-level as well as instruction-level parallelism. As the two techniques are complementary, they are sometimes combined in systems with multiple multithreading CPUs and in CPUs with multiple multithreading cores.
NAS
Network-attached storage (NAS) is file-level computer data storage connected to a computer network providing data access to heterogeneous network clients. A NAS unit is essentially a self-contained computer connected to a network, with the sole purpose of supplying file-based data storage services to other devices on the network. The operating system and other software on the NAS unit provide the functionality of data storage, file systems, and access to files, and the management of these functionalities. The unit is not designed to carry out general-purpose computing tasks, although it may technically be possible to run other software on it. NAS units usually do not have a keyboard or display, and are controlled and configured over the network, often by connecting a browser to their network address. The alternative to NAS storage on a network is to use a computer as a file server. In its most basic form a dedicated file server is no more than a NAS unit with keyboard and display and an operating system which, while optimised for providing storage services, can run other tasks; however, file servers are increasingly used to supply other functionality, such as supplying database services, email services, and so on.
Native
The uncompressed storage capacity of storage media and hardware is known as native capacity.
NDMP
The Network Data Management Protocol (NDMP) is an open protocol for enterprise-wide network based data management. NDMP defines a network-based mechanism and protocol for controlling backup, recovery, and other transfers of data between primary and secondary storage.
NEBS
NEBS (Network Equipment-Building System) describes the environment of a typical United States RBOC Central Office. NEBS is the most common set of safety, spatial and environmental design guidelines applied to telecommunications equipment in the United States. It is an industry requirement. It is not a legal requirement. NEBS was developed by Bell Labs in the 1970s to standardize equipment that would be installed in a central office. The objective was to make it easier for a vendor to design equipment compatible with a typical Regional Bell Operating Company (RBOC) central office (CO). This would result in lower development costs and ease the equipment's introduction into the network. Telcordia now manages the NEBS specifications. The four largest US Telecommunications companies (AT&T, Verizon, BellSouth, and Qwest) created the Telecommunications Carrier Group (TCG), a group formed to synchronize NEBS standards across the industry in the US. The TCG checklist specifies the individual NEBS requirements of each of its members in a matrix, making it simple to compare them.
There are 3 Levels:
"NEBS Level 1" means a very low threshold of equipment hazards and network degradation. NEBS Level 1 addresses the personnel and equipment safety requirements of GR-63-CORE and GR-1089-CORE. Operability requirements are not enforced for NEBS Level 1 certification. It is primarily used for getting prototypes into lab trials. RBOCs require all equipment deployed by CLECs to be NEBS Level 1 certified.
"NEBS Level 2" addresses equipment operability in a controlled environment (usually datacenters) that will not be subjected to environmental stress. Due to ambiguity, this level of certification is rarely (if ever) used.
"NEBS Level 3" is a term from Bellcore special report, SR-3580, and means the equipment meets all of the requirements of GR-63-CORE and GR-1089-CORE. NEBS Level 3 has strict specifications for fire suppression, thermal margin testing, vibration resistance (earthquakes), airflow patterns, acoustic limits, failover and partial operational requirements (such as chassis fan failures), failure severity levels, RF emissions and tolerances, and testing/certification requirements.
OEM
Original equipment manufacturer, or OEM, is an ambiguous and abstruse phrase used in relation to the manufacturing and marketing of products. Usage of the phrase is not consistent, but it typically relates to a situation in which one company uses a component made by a second company in its own product, or sells the product of the second company under its own brand.
Operating safety
In connection with a server the term "operating safety" is directly associated with "availability of data" and "availability of data-processing". This is only a given, if the server resp. the computing system provides the requested data in realtime (online). With a operating safety of 100 % a system is able to provide or process the requested data at any time. Even though a 100 % operating system is not possible with today's technology, there exist computing-structures which can guarantee data-security of 99,9 %, such as RAID-, Clustering- or SAN-systems.
Parity
a data-redundance used with RAID-levels 2, 3, 4 und 5.
PCI
The Peripheral Component Interconnect, or PCI Standard (commonly PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard.
Peripherie
Term for all input and output hardware connected to a computer, such as printer, monitor, mouse or drives.
PetaByte, PByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
PIO
Programmed input/output (PIO) is a method of transferring data between the CPU and a peripheral such as a network adapter or an ATA storage device.
QIC
Quarter inch cartridge tape (abbreviated QIC, commonly pronounced "quick") is a magnetic tape data storage format introduced by 3M in 1972, with derivatives still in use as of 2007. QIC comes in a rugged enclosed package of aluminum and plastic that holds two tape reels driven by a single belt in direct contact with the tape. The tape was originally one quarter inch (1/4") wide and anywhere from 300 to 1500 feet long. Data is written to tape in linear tracks in what is called "serpentine" mode, where the tracks alternate direction by use of a head switch or step. Since the introduction of the format, QIC has been widely used and many variations exist. There is a QIC trade association that publishes QIC standards which include interfaces and logical formats, to a very large extent it was the efficiency and openness of this organisation which encouraged hardware and software developers to use this type of drive and media.
RAID
RAID — which stands for Redundant Array of Inexpensive Disks (as named by the inventor) or occasionally known as Redundant Array of Independent Disks (a name which later developed within the computing industry) — is a technology that employs the simultaneous use of two or more hard disc drives to achieve greater levels of performance, reliability, and/or larger data volume sizes. The phrase "RAID" is an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disc drives. RAID's various designs all involve two key design goals: increased data reliability and increased input/output performance. When several physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across several disks, but the array is seen by the computer user and operating system as one single disk.
RAID 0
RAID 0 is in principle no full RAID-level, as it isn't redundant. RAID 0 (also known as a stripe set or striped volume) splits data evenly across two or more disks (striped) with no parity information for redundancy. It is important to note that RAID 0 was not one of the original RAID levels and provides zero data redundancy. RAID 0 is normally used to increase performance, although it can also be used as a way to create a small number of large virtual disks out of a large number of small physical ones.
RAID 1
RAID 1 creates an exact copy (or mirror) of a set of data on two or more disks. This is useful when read performance or reliability are more important than data storage capacity. Such an array can only be as big as the smallest member disk. A classic RAID 1 mirrored pair contains two disks (see diagram), which increases reliability geometrically over a single disk. Since each member contains a complete copy of the data, and can be addressed independently, ordinary wear-and-tear reliability is raised by the power of the number of self-contained copies.
RAID 10
RAID 1+0, sometimes called RAID 1&0, or RAID 10, is similar to a RAID 0+1 with exception that the RAID levels used are reversed — RAID 10 is a stripe of mirrors. Below is an example where three collections of 120 GB level 1 arrays are striped together to make 360 GB of total storage space.
RAID 2
RAID 2 stripes data at the bit (rather than block) level, and uses a Hamming code for error correction. The disks are synchronized by the controller to spin in perfect tandem. Extremely high data transfer rates are possible. This is the only original level of RAID that is not currently used. The use of the Hamming(7,4) code (four data bits plus three parity bits) also permits using 7 disks in RAID 2, with 4 being used for data storage and 3 being used for error correction. RAID 2 is the only standard RAID level, other than some implementations of RAID-6, which can automatically recover accurate data from single-bit corruption in data. Other RAID levels can detect single-bit corruption in data, or can sometimes reconstruct missing data, but cannot reliably resolve contradictions between parity bits and data bits without human intervention. (Multiple-bit corruption is possible though extremely rare. RAID 2 can detect but not repair double-bit corruption.). At the present time, there are no commercial implementations of RAID-2
RAID 3
RAID 3 uses byte-level striping with a dedicated parity disk. RAID 3 is very rare in practice. One of the side-effects of RAID 3 is that it generally cannot service multiple requests simultaneously. This comes about because any single block of data will, by definition, be spread across all members of the set and will reside in the same location. So, any I/O operation requires activity on every disk and usually requires synchronized spindles. In our example, a request for block "A" consisting of bytes A1-A6 would require all three data disks to seek to the beginning (A1) and reply with their contents. A simultaneous request for block B would have to wait..
RAID 30
RAID 30 was developed by AMI and presents the striped variant of RAID 3. It provides data security, a high performance and is ideal for sequential transfer of large files. RAID 30 requires at least six harddrives and is rarly used. \
RAID 4
RAID 4 uses block-level striping with a dedicated parity disk. This allows each member of the set to act independently when only a single block is requested. If the disk controller allows it, a RAID 4 set can service multiple read requests simultaneously. RAID 4 looks similar to RAID 5 except that it does not use distributed parity, and similar to RAID 3 except that it stripes at the block level, rather than the byte level. Generally, RAID 4 is implemented with hardware support for parity calculations, and a minimum of 3 disks is required for a complete RAID 4 configuration. In the example on the right, a read request for block "A1" would be serviced by disk 0. A simultaneous read request for block B1 would have to wait, but a read request for B2 could be serviced concurrently by disk 1.
RAID 5
RAID 5 uses block-level striping with parity data distributed across all member disks. RAID 5 has achieved popularity due to its low cost of redundancy. This can be seen by comparing the number of drives needed to achieve a given capacity. RAID 1 or RAID 0+1, which yield redundancy, give only s/2 storage capacity, where s is the sum of the capacities of n drives used. In RAID 5, the yield is s * (n - 1)/n. Using 1 TB drives as an example, four of them can build a 2 TB redundant array under RAID 1 or RAID 1+0, but they can be used to build a 3 TB array under RAID 5. Although RAID 5 is commonly implemented in a disk controller, some with hardware support for parity calculations (Hardware raid cards) and some using the main system processor (Motherboard based raid controllers), it can also be done at the operating system level using Windows "Dynamic Disks" or with mdadm in Linux. A minimum of 3 disks is required for a complete RAID 5 configuration. In some implementations a degraded RAID 5 disk set can be made (3 disk set of which only 2 are online). In the example on the right, a read request for block "A1" would be serviced by disk 0. A simultaneous read request for block B1 would have to wait, but a read request for B2 could be serviced concurrently by disk 1.
RAID 50
RAID 50 was developed by AMI and presents the striped version of RAID 5 and is recommend when besides data security and fast access also a high transferrate is needed. RAID 50 needs at least six harddrives and is seldom used.
RAID 51
RAID 51 (also called RAID 15) corresponds to a mirrored RAID 5. The speed is similar to a RAID-5-array. This arrangement reaches a very high data security but has no relevance in practice.
RAID 7
RAID 7 is a trademark of Storage Computer Corporation. It adds caching to a derivative of RAID 3 and RAID 4 to improve performance.
RAIDn
RAIDn was developed by the Californian company Inostor, a daughter of Tandberg Data. RAIDn presents an algorithm that guarantees a higher system stability for harddrive-arrays than RAID-solutions so far. Standard RAIDs compensate the failor of a harddrive. With RAIDn the user is free to define the amount of drives that are allowed to fail. In using, for example, 10 harddrives, RAIDn makes it possible to recover date of any amount of failed drives with only three standy drives. So with the same hardware there are 7 instead of 4 (with RAID 5+1) usable disks available. According to Tandberg the costs for data security are reduced by 30 to 50 %.
Redundant
Duplicated drive or component, to increase data and system stability.
Remote Access
Pertaining to communication with a data processing facility from a remote location or facility through a data link. One of the more common methods of providing this type of remote access is using a VPN
S.M.A.R.T
Self-Monitoring, Analysis, and Reporting Technology, or S.M.A.R.T., is a monitoring system for computer hard discs to detect and report on various indicators of reliability, in the hope of anticipating failures.
S-AIT
Advanced Intelligent Tape (AIT) is a high-speed, high-capacity magnetic tape data storage format developed and controlled by Sony. It competes mainly against the DLT, LTO, DAT/DDS, and VXA formats. AIT uses a cassette similar to Video8. Super AIT (S-AIT) is a higher capacity variant using wider tape in a larger, single-spool cartridge. Both AIT and SAIT use the helical scan method of reading and writing the tape
SAN
Storage area network (SAN) is an architecture to attach remote computer storage devices (such as disk arrays, tape libraries and optical jukeboxes) to servers in such a way that, to the operating system, the devices appear as locally attached. Although cost and complexity are dropping, as of 2007, SANs are still uncommon outside larger enterprises. By contrast to a SAN, Network Attached Storage (NAS) uses file-based protocols such as NFS or SMB/CIFS where it is clear that the storage is remote, and computers request a portion of an abstract file rather than a disk block
SAN-Management + Bluefin
Cooperation of components within a heterogenous Storage Area Network (SAN) today is nearly completely guaranteed. However producers face the challenge to unify the administration of network nodes, data and access authorizations as well as the surveillance and security of data transfer - independent of hardware, operating systems and applications. As within LANs there was no demand for administration of storage devices, the backlog for SANs is high. A complete strategy for this problem is the "Bluefin"-specification of SNIA. Bluefin defines a general gateway for administration of storage-nets. It ought to identify and classify objects according to consistent criteria. Real and virtual resources in the company can be monitored as well and be transmitted by using a shared transport-mechanism. Bluefin therewith is the project name for far more than an API (Application Programming Interface).
SCSI
Small Computer System Interface, or SCSI, is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard discs and tape drives, but it can connect a wide range of other devices, including scanners and CD drives. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.
SCSI-1
SCSI-1 defines the basics of the first SCSI buses, including cable length, signaling characteristics, commands and transfer modes. It was quite limited, especially by today's standards, and defined only the most fundamental of SCSI features and transfer modes. Devices corresponding to the SCSI-1 standard use only a narrow (8-bit) bus, with a 5 MB/s maximum transfer rate. Only single-ended transmission was supported, with passive termination. There were also difficulties associated with the standard gaining universal acceptance, due to the fact that many manufacturers implemented different subsets of its features. The standard did not call for all devices to implement support for the same commands, so there was no guarantee that any given device would work with any other! SCSI-1 is now obsolete, and the standard has in fact been withdrawn by ANSI. Devices that adhere to the SCSI-1 standard can in most cases be used with host adapters and other devices that use the higher transfer rates of the more advanced SCSI-2 protocols, but they will still function at their original slow speed.
SCSI-2
SCSI-2 is the successor of SCSI-1. Requirements for different periphery-hardware like CD-ROM-drives are specified more thoroughly. Furthermore the standard contains the options Fast and Wide.
SCSI-2 Fast
SCSI-2 Fast can transfer data with a speed of 10 MBytes/second twice as fast as SCSI-2. Furtheron a 8-Bit-data-bus is used and the amount of devices to be connected stays constant at seven. Cable length can be 3 meters max.
SCSI-3
SCSI-3 uses a serial data transfer. Offsets are SSA (20 MByte/s), Fibre Channel (100 MByte/s) und IEEE-1394 (Firewire).
Serial ATA (SATA)
Serial Advanced Technology Attachment (SATA) is a computer bus primarily designed for transfer of data between a computer and mass storage devices such as hard disc drives and optical drives. The main advantages over the older parallel ATA interface are faster data transfer, ability to remove or add devices while operating (hot swapping), thinner cables that let air cooling work more efficiently, and more reliable operation with tighter data integrity checks. It was designed as a successor to the Advanced Technology Attachment standard (ATA), and is expected to eventually replace the older technology (retroactively renamed Parallel ATA or PATA). Serial ATA adapters and devices communicate over a high-speed serial cable.
Serial Attached SCSI (SAS)
Serial Attached SCSI (SAS) is a data transfer technology designed to move data to and from computer storage devices such as hard drives and tape drives. It is a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in corporate data centers, and uses the standard SCSI command set. At present it is slightly slower than the final parallel SCSI implementation, but in 2009 it will double its present speed to 6 Gbit/s, allowing for much higher speed data transfers than previously available, and is "downwards"-compatible with second generation SATA drives. SATA 3.0Gbps drives may be connected to SAS backplanes, but SAS drives may not be connected to SATA backplanes. The SAS protocol is developed and maintained by the T10 technical committee of the International Committee for Information Technology Standards (INCITS) and promoted by the SCSI Trade Association (SCSITA).
SLR
Scalable Linear Recording is the name used by TANDBERG DATA for its line of QIC based tape drives. The earliest SLR drive, the SLR1, has a capacity of 250 MB, while the latest drive, the SLR400, has a capacity of 200 GB. The term SLR is now often used to refer to QIC tapes, as they are the only drives still manufactured that use them.
SNIA
An association of producers and consumers of storage networking products, whose goal is to further storage networking technology and applications. The Storage Networking Industry Association, or SNIA, was incorporated in December, 1997, and is a registered 501-C6 non-profit trade association. Its members are dedicated to "ensuring that storage networks become complete and trusted solutions across the IT community". The SNIA works towards this goal by forming and sponsoring technical work groups, by producing (with strategic partner Computerworld) the Storage Networking World conference series, by building and maintaining a vendor neutral Technology Center in Colorado Springs, and by promoting activities that expand the breadth and quality of the storage networking market>.
Tape Library
A tape library, sometimes called a tape silo, or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes (a robot).
Tape-Autoloader
A system unit consistion of a tape drive and a certain amount of storing positions for Data Cartridges. Besides a streamer mostly 8, 10 or 16 slots for cartridges are provided. The capacity of the complete device results from the amount of storing positions multiplied by the capacity of the streamer.
Tape-Automation
An autoloader or a tape-library is an automatic system to load or anload a certain amount of Data Cartridges automatically by mechanical means to one or more tape drives. The streamer, the mechanics and the storing slots for the Data Cartridges form their own system unit. This is connected with the server through a computer-interface like SCSI and controlled and operated by software.
Tapeless Backup
Basic idea of Tapeless Backup is a disconnection of productive data and their backup-application from the original archive system. So called disc backup systems are positioned between classic tape-archives and mirrored resp. replicated storage solutions. Basically a disk-based subsystem is positioned between archive application and tape-archive. The backup-software saves the data as usual, but to harddrives. Through elimination of the file-system the process is supposed to become easier and faster. The higher data flow rate should also reduce the backup-time. From the harddisk the administration can always archive data to tape cassettes or optical media as needed.
Tape-Library
A tape library, sometimes called a tape silo, or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes (a robot). One of the earliest examples was the IBM 3850 Mass Storage System (MSS), announced in 1974. These devices can store immense amounts of data, currently ranging from 20 terabytes up to more than 50 petabytes of data, or about one hundred thousand times the capacity of a typical hard drive and well in excess of capacities achievable with network attached storage. Typical entry-level solutions cost around $10,000 USD, while high-end solutions can cost in excess of $70,000 USD. For large data-storage, they are a cost-effective solution, with cost per gigabyte as low as 10 cents USD, or at least 60% less than most hard drives, and they also provide systematic access to very large quantities of data. The tradeoff for their larger capacity is their slower access time, which usually involves mechanical manipulation of tapes. Access to data in a library takes from several seconds to several minutes. Because of their slow random access and huge capacity, tape libraries are primarily used for backups and as the final stage of digital archiving. A typical application of the latter would be organization's extensive transaction record for legal or auditing purposes. Another example is hierarchical storage management (HSM), in which tape library is used to hold rarely used files from file systems. Smaller tape libraries with only one drive and robot are known as autoloaders.
TeraByte, TByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions
Terminator
Electrical termination of a signal involves providing a terminator at the end of a wire or cable to prevent an RF signal from being reflected back from the end, causing interference. The terminator is placed at the end of a transmission line or daisy chain bus (such as in SCSI), designed to match impedance and hence minimize signal reflections.
Travan
Travan is an 8 mm magnetic tape cartridge design developed by the 3M company, used for thestorage of data in computer backups and mass storage. Over time, subsequent versions of Travan cartridges and drives have been developed that provide greater data capacity, while retaining the standard 8 mm width and 750' length. Travan is standardized under the QIC body. The Travan format competes mainly against the DDS, AIT, and VXA formats.
Ultra Density Optical (UDO)
An Ultra Density Optical disc or UDO is a 133.35 mm (5.25") ISO cartridge optical disc which can store up to 120 GB of data. Utilising a design based on a Magneto-optical disc, but using Phase Change technology combined with a blue violet laser, a UDO disc can store substantially more data than a magneto-optical disc or MO, because of the shorter wavelength (405 nm) of the blue-violet laser employed. MOs use a 650 nm-wavelength red laser. Because its beam width is shorter when burning to a disc than a red-laser for MO, a blue-violet laser allows more information to be stored digitally in the same amount of space.
Ultra160-SCSI
Ultra160 SCSI provides SCSI bus maximum burst data rates of 160 Mbytes/sec. That is double the Ultra2 LVD drives (80 Mbytes/sec), quadruple the fastest SCSI-2 standard (40 Mbytes/sec), and light years ahead of the SCSI-1 standard used prior to 1992 in which SCSI bus rates were as slow as 3 Mbytes/sec. More realistically, sustained data transfer rates of 30-50 Mbytes/sec can be expected. This increased bandwidth means optimal performance for server environments where rapid response is required and random access and large queues are the norm. When using applications such as CAD and CAM, digital video, and any RAID environment, the increased bandwidth is immediately noticeable as information moves quickly and effortlessly.
Ultra2-SCSI
A form of SCSI capable of 40 megatransfers per second. There is no single ended Ultra2 SCSI specification. Low voltage differential (LVD) Ultra2 SCSI supports bus lengths of up to 12 meters. High voltage differential Ultra2 SCSI supports bus lengths of up to 25 meters. Ultra2 SCSI specifications define both narrow (8 data bits) and wide (16 data bits) buses. A narrow Ultra SCSI bus transfers data at a maximum of 40 MBytes per second. A wide Ultra2 SCSI bus transfers data at a maximum of 80 MBytes per second.
Ultra320-SCSI
Utra320 SCSI is the seventh generation of SCSI I/O technology. Its dominant feature is its increased speed of 320 MBytes per second. Other features include; paced data transfer, a free running clock, a training pattern at the beginning of a transfer series, skew compensation, driver pre-compensation and/or optional receiver Adjustable Active Filter (AAF). Ultra320 SCSI devices all support packetized protocol and may support Quick Arbitration and Selection (QAS). Expander communications techniques have also been defined.
Ultra-SCSI
A form of SCSI capable of 20 megatransfers per second. Single ended Ultra SCSI supports bus lengths of up to 1.5 meters. Differential Ultra SCSI supports bus lengths of up to 25 meters. Ultra SCSI specifications define both narrow (8 data bits) and wide (16 data bits) buses. A narrow Ultra SCSI bus transfers data at a maximum of 20 MBytes per second. A wide Ultra SCSI bus transfers data at a maximum of 40 MBytes per second.
USB
Universal Serial Bus (USB) is a serial bus standard to interface devices. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve the plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the computer (hot swapping). Other convenient features include providing power to low-consumption devices without the need for an external power supply and allowing many devices to be used without requiring manufacturer specific, individual device drivers to be installed. USB is intended to help retire all legacy varieties of serial and parallel ports. USB can connect computer peripherals such as computer mouse, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives. For many of those devices USB has become the standard connection method. USB was originally designed for personal computers, but it has become commonplace on other devices such as PDAs and video game consoles. As of 2008, there are about 2 billion USB devices in the world.
Virtualization
Virtualization devides the logical view on data and data storage medium from the physical unit. It inables the user to view his storage resources in SAN independently of their physical location. A logical interface makes a central administration of storage systems possible for the administrator. Furthermore it communicates with the physical storage devices, whereas the logical or virtual devices reference to the physical systems. Advantage is a significantly better storage utilization, better management of capacities, easy exchange of physical units (disks or arrays) as well as independence of physical devices.
VXA
VXA is a tape backup format originally created by Ecrix and now owned by TANDBERG DATA. After the merger between Ecrix and Exabyte, VXA was produced by Exabyte Corporation. On November 20, 2006, Exabyte was purchased by Tandberg Data. Exabyte and Ecrix describe the data format as "packet" technology as opposed to "linear" technology. This is a variation on helical scan technology. Instead of writing data in continuous, predefined linear tracks, data is written in addressable packets along the tape. The claim is that this gives better reliability and error recovery as well as being able to adapt to different data rates. The VXA format competes mainly against the DDS, SLR, AIT, & DLT-V formats.
Warm Swap
Term used to describe the method of swapping a device in a computer while the computer is in a suspend mode such as hibernate.
Wide SCSI
Wide SCSI refers to devices that use a standard-speed, 5 MHz SCSI bus but on a wide, 16-bit bus. It is also sometimes called Wide SCSI-2 after the standard that defined it.
Write-back Cache
A caching method in which modifications to data in the cache aren't copied to the cache source until absolutely necessary. Write-back caching is available on many microprocessors, including all Intel processors since the 80486. With these microprocessors, data modifications (e.g., write operations) to data stored in the L1 cache aren't copied to main memory until absolutely necessary. In contrast, a write-through cache performs all write operations in parallel -- data is written to main memory and the L1 cache simultaneously. Write-back caching yields somewhat better performance than write-through caching because it reduces the number of write operations to main memory. With this performance improvement comes a slight risk that data may be lost if the system crashes. A write-back cache is also called a copy-back cache.
Write-trough Cache
A disk or memory cache that supports the caching of writing. Data written by the CPU to memory or to disk is also written into the cache. Write performance is not improved with this method. However, if a subsequent read operation needs that same data, read performance is improved, because the data are already in the high-speed cache.
YotaByte, YByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions.
ZetaByte, ZByte
Byte is a unit of measurement of information storage, most often consisting of eight bits.
8 Bits equal 1 Byte, 1.024 Bytes = 1 Kilobyte (KB, KByte), 1.024 KB = 1 Megabyte (MB, MByte), 1.024 MB = 1 Gigabyte (GB, GByte) and 1.024 GB = 1 Terabyte (TB, TByte). The subsequent units are: Petabyte (PT, PByte), Exabyte (EB, EByte), Zetabyte (ZB, ZByte) and Yotabyte (YB, YByte). Harddrive-producers use for calculation of capacities a size that is based on a wrong conversion value: 1.000 Byte = 1 Kilobyte (KB), 1.000 KB = 1 Megabyte (MB) etc. This is also often used by the media for simplification. Exabyte is also the name of a US-producer of network backup systems and intelligent, automated data-backup-solutions

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