Glossary of Terms

"A comprehensive glossary of data management and storage terms which ARE updated and Enhanced regularly"

AIT – Advanced Intelligent Tape
AIT is magnetic tape technology, similar in appearance to an 8mm Exabyte tape. The cartridges use a helical scan recording method and consist of an advanced metal evaporated tape, which provides greater density than other types of magnetic tape. AIT media also include a Memory-In-Cassette (MIC) feature, which stores tape status and indexing information. They have native capacities of 50GB (AIT-2), 100GB (AIT-3) and 200GB (AIT-4). Super AIT (SAIT) uses half-inch cartridges with native capacities of 500GB (SAIT-1) and 1TB (SAIT-2).

Archiving
The process of removing infrequently used data from the current network storage area and keeping it in a specifically designed area where it can be easily and quickly retrieved.

Bit
Bit is short for binary digit and it is a single numeric character which can hold only one of two values: 0 or 1. A bit is the smallest unit of information on a computer.

Buffer
Part of RAM used for temporary storage of data that is waiting to be sent to a device; used to compensate for differences in the rate of flow of data between components of a computer system, interface or peripheral.

Byte
A byte is composed of 8 consecutive bits.

Clean Room
A clean room is an area in which the air quality, temperature and humidity are highly regulated and monitored in order to protect sensitive equipment from contamination. The air in a clean room is repeatedly filtered to remove dust particles and other impurities that can damage the production of highly sensitive technologies.

The measure of the air quality of a clean room is described in Federal Standard 209. Clean rooms are rated as "Class 10,000," where there exists no more than 10,000 particles larger than 0.5 microns in any given cubic foot of air; "Class 1000," where there exists no more than 1000 particles; and "Class 100," where there exists no more than 100 particles. Hard disk drive fabrication requires a Class 100 clean room.

Degaussing
To degauss a magnetic storage medium is to remove all data stored on it by demagnetising it. A degausser is a machine that is used for this purpose.

DLT -Digital Linear Tape
DLT is a magnetic data storage tape and drive system that uses half inch linear recording in a single hub cartridge. It uses a special compression method, known as Digital Lempel Ziv 1 (DLZ1), which enables the storage and retrieval of data at high speeds and in large volumes.

Drive Motor
The drive motor spins the platters in a hard disk drive, with modern hard disk motors able to spin platters at speeds from 5 000rpm to 15 000rpm. The higher the revolutions the lower the seek time on a disk. In other words, the faster the disk motor the faster the disk. The speed of the motor is however limited by the speed of the interface with SATA and SCSI the leaders at this point.

DropOut
Refers to the signal loss caused by a tape head clog, defect in the tape, debris, or other feature that causes an increase in the head-to-tape spacing. A dropout can also be caused by missing magnetic material, faulty head or bad signals and transfers via an interface.

EOD – End of Data
EOD is an electronic or magnetic marker (or series of markers) which indicates that the data contained on a tape has reached its end. An EOD indicates that no further information is recorded past this point.

EOD – End of Partition 
EOP is an electronic or magnetic marker indicates where one of many possible logical volumes on a tape ends. An EOP marker would generally be followed by a BOP on a tape with multiple partitions.

EOT – End of Tape
EOT is a magnetic or electronic indicator which signals the end of tape/transmission.

File
A file is a collection of data or information which has a name and that is capable of being manipulated as an entity. Some examples of types of files are data files, text files and program files.

Head Assembly
The head assembly is comprised of a single or multiple read/write heads connected to the disk arm which in turn is attached to the disk’s actuator. The entire assembly moves in order to enable the read/write heads to access the requires sections of the disk platter.

Head Crash
When the read/write head of a hard disk makes contact with the platter surface. This can be an outcome of either component failure or debris on the platter, resulting in the disk head dragging or bouncing on the platter surface. Given that modern hard disks operate between 5 000rpm and 15 000rpm the damage can be quite extensive when the head makes contact with the media surface and will result in data recovery being not viable in the majority of cases.

Header
A header is generally a record, file or block at the start of data that can contain information such as the tape name, date, time, recorded format, length etc. Not all tapes have headers although most tapes created by backup software will tend to have one

Helical Scan
Helical scan is a method of recording data onto a slow moving magnetic tape and uses a rapidly rotating read/write head. The data is recorded onto diagonal tracks, which are at an angle to the edge of the tape. After loading into a drive, the tape is pulled from the cartridge and wrapped around the read/write head, which rotates at around 30 metres per second.

High Voltage Differential
(HVD) SCSI interface predominantly associated with large scale enterprise tape drives. Power consumption is 5.0Volts and over.

Interface
A term used for a descriptive common boundary between peripheral and computer system, can also be a piece of software to interact with to control such peripherals or computer system.

LAN – Local Area Network
A LAN is a data communication system whereby a group of computers and peripheral devices are linked together within a confined geographic area and are set up to share a common environment. Ethernet, FDDI and now wireless technologies are examples of standard LANs. A LAN may be used from two users upwards to many thousand.

Leader Block
The beginning of nearly all high density tape has a 'leader' structure of some description. The 'block' is found on such cartridges as 34XX and 35XX cartridges to name a couple and is generally a plastic oblong shaped device which holds the beginning of the tape. It serves a purpose to feed tape in and out of the cartridge generally guided through a tape path.

Logical Recovery
A logical recovery utilises software tools in order to recover data. In these cases the hard disk is still within its operational parameters, however the data is in accessible. This can be due to boot problems, data corruption or some form of malware.

Longitudinal Recording
Longitudinal recording is a method of recording data whereby tape is passed by a non-moving recording head. The tracks are recorded parallel to the tape edge.

Low Voltage Differential
(LVD) SCSI Interface now predominantly found on SME tape drives, disk drives and equipment. Power consumption is around 3.3V, most times less than 5.0V.

LTO - Linear Tape Open
LTO is an open format tape storage technology developed by Hewlett-Packard (HP), IBM, and Certance. The term "open-format" means that users have access to multiple sources of storage media products that will be compatible. The high capacity implementation of LTO technology is known as the LTO Ultrium format, or simply LTO Ultrium.

The LTO Ultrium technology has evolved through several generations.The latest of these is Generation 3, which became available in late 2004 and provides data storage capacity of up to 800 gigabytes (GB) and a maximum transfer rate of 80 to 160 megabytes per second (MB/s). Generations 4, 5, and 6 are currently under development. Generation 4 is planned to provide a maximum storage capacity of 1.6 terabytes (TB) and a transfer rate of up to 240 MB/s. Generation 5 is expected to have a maximum storage capacity of 3.2 TB and a transfer rate of up to 360 MB/s. Generation 6 is expected to have a maximum storage capacity of 6.4 TB and a transfer rate of up to 540 MB/s. (All of these capacity and transfer speed figures are based on 2:1 data compression).

Magnetic Media
Magnetic Media refers to any form of data storage device (tape or disk) which uses a magnetic surface for storing information and data.

Magnetic Tape
Magnetic Tape refers to plastic flexible tape coated on one side with ferromagnetic material which is used for storing information and data. It is a sequential storage medium and is generally used for data backup and archiving purposes. Magnetic tape originally took the form of open reels (such as 9 & 21 track tapes) but have been superseded by cartridges and cassettes of many sizes and shapes.

Mammoth
Mammoth is an integrated 8mm magnetic tape storage technology that uses advanced data management features such as advanced metal evaporated (AME) media to improve data recording performance. Mammoth tape drives are designed to be used in a continuous 24/7 environment.

Media Migration
Media migration is the movement of data from one type of storage media to another data storage medium. This is usually carried out due to the adoption of a more technologically advanced data storage and backup technology and usually means a reduction in storage space due to a higher density media than previously used.

NAS –Network Attached Storage
A NAS is not to be confused with a SAN, main difference is that a NAS binds to an already existing LAN and is generally a'pool' of storage mediums in one device. Some forms of NAS can be a JBOD (Just a Bunch of Disk), SCSI RAID array, tape subsystem or a straight disk pool confined in a single device. Once again a NAS can be accessed via any server, PC or peripheral on the LAN.

Native Capacity
Native capacity refers to the total storage volume available on a particular media type if data is written to it without any compression.

Optical Media
Optical media is a form of data storage that uses polycarbonate material to store digital information. The data is accessed and read using laser diode technology. Optical media generally comes in three forms - ROM (read only), WORM (write once read many), and RW (re-writeable).

Physical Recovery
A physical recovery involves component failure within the disk. The disk would require the repair or replacement of components in order to restore the disk to within its operational parameters. From here a Recovery Technician can temporarily gain access in order to recover data.

Platter
The physical disk with a hard disk drive. Normally composed of metal or glass the platters are coated with thin film oxide to store magnetic data. Hard disks can have a single or multiple platters dependant on the disk’s age and capacity.

Platter Swap
Involves the platters from one disk being transplanted from its chassis into that of an identical disk. This procedure is performed in the case of malfunctioning disk components. Provided there is no media damage the platter from the original disk can be transposed into an identical ‘donor’ disk. This allows the original platters to be accessed utilising the functional components of the donor disk.

QIC - Quarter Inch Cartridge
QIC is a magnetic tape technology that was developed in the 1980’s and used mainly for backup data storage purposes. There are two types – full size data cartridge and mini cartridge.

RAID – Redundant Array of Independent Disks
RAID is a disk drive subsystem that uses two or more hard disks and a RAID disk controller in order to increase performance while at the same time provide fault tolerance. They are usually implemented in a server based environment using specialised software and/or hardware, however in more recent times desktop PCs are increasingly incorporating RAID disk systems with the addition of an onboard RAID controller and additional IDE, SATA or SCSI disks.

RAID can improve performance due to "Disk Striping", a process which allows multiple disks to read and write simultaneously. RAID systems can provide fault tolerance by processes called "Data Mirroring" and "Data Parity" – whereby data is entirely copied onto two drives and can be used to rebuild lost data when a drive fails.

There are a number of different RAID levels ranging from Level 0 – Level 10 and RAID subsystems come in various sizes from small desktop models to floor-standing models.

Read/Write Head
This is the component that at interprets or manipulates the thin film oxide on the platter’s surface in order for data to be read or written on the disk. In the case of hard disks the head ‘flies’ mere nanometres from the platter surface not making contact with the media, where as tape media does.

SAN – Storage Area Network
A SAN is a dedicated network of computer storage devices and servers which are connected at high speed. A SAN is structured in such a way that all storage devices (such as tape libraries and disk arrays) attached to the SAN are accessible from any server on the network and therefore provide consolidated storage management facilities.

SCSI - Small Computer Systems Interface
SCSI is the general interface of choice for most tape and disk drives plus peripherals.

SDLT - Super Digital Linear Tape
SDLT is magnetic tape drive technology that uses half inch linear recording in a single hub cartridge. It is a variant of DLT technology which was developed to increase (double) native and compressed cartridge capacity. Also see DLT.

Serpentine Linear
Serpentine linear refers to a magnetic recording format whereby data is recorded in along the length of the tape in a linear fashion from one end of the tape to the other, and back.

SLR – Scalable Linear Recording
SLR is a range of magnetic tape drive technology that evolved from QIC (Quarter Inch Cartridge) media technology.

Tape
Tape is a specialised strip of plastic, which has been magnetically coated to enable data to be encoded and recorded onto it.

Tape Drive
A tape drive is a computer peripheral that allows data to be read from and written to magnetic tape. Tape drives are frequently used for data backup and archiving purposes. Generally they are a sequential storage medium which means that they must read all data from beginning to end in order to read a specific piece of data.

VXA
VXA is a revolutionary 4mm tape drive technology which uses patented "packet" technology. This technology enables data to be read and written in packets - the same way that it is done on the internet. It is an extremely secure way to store, archive, retrieve, and exchange data and provides dramatically higher capacity and speed to other products at the same price level.

3590
3590 (Magstar) technology is a high capacity, high performance magnetic tape technology developed by IBM. It has gained wide acceptance and implantation in the marketplace by providing reliability and fast access to the midrange data centre/enterprise class and includes features such as Error Correction Code (ECC), servo track mechanisms, resident diagnostics, redundant parity checking, and read after write verification.

3592
3592 Jaguar tape technology offers significant improvements in speed, capacity and transfer rates to the enterprise level user over 3590. It provides both fast access to and retrieval of data as well as high capacity backup capability, a combination which was not available at the time of the 3592’s introduction. The 3592 tape drive also offers WORM (Write Once Ready Many) functionality.