- GLOSSARY
QIC Tape Technology
Compiled by Jane Hassler
append when data is written after previously recorded data, as opposed to overwriting the previously recorded data ... useful in providing audit trails in file-by-file backup
archive long term on- and/or off-site storage
areal density number of flux transitions per square unit of recordable area, or bits per square inch
average backup rate number of megabytes per minute which can be transferred from the hard drive to the tape drive; this can be influenced by type of computer, tape drive and compression
autochanger a device under system control allowing automatic access to multiple tape cartridges, enabling unattended backup of larger disk capacities
backup copying information from a hard disk onto another data storage medium
backward compatibility the ability of a current product to read tapes written on earlier drives and, if so specified, to write tapes in the same format
baud data transmission speed, in bits per second
bit smallest amount of data that can be processed by a computer; can be represented as either zero or one block consists of a number of bytes ... block sizes vary ... commonly used sizes are 512 or 1024 data bytes
BOP (beginning of partition) on tapes partitioned into logical volumes, the BOP is treated as the Beginning of Tape (BOT) for that volume. A tape has only one BOT, but has as many BOPs as partitions
BOT (beginning of tape) designated by a specific hole pattern on quarter-inch cartridge tape media
BPI (bits per inch) the number of data bits recorded on one track per inch of tape
buffer a temporary storage area in which the processor places information so that a second device, working at a different speed, can find the information when needed
byte eight bits treated as a unit and representing a character
capacity total amount of user data that can be stored on a device
_ compressed effective capacity after data has been processed to reduce storage space required while maintaining data integrity ... software and hardware compression are available
_ uncompressed capacity for data that has not been processed to reduce the effective size or volume; sometimes referred to as native
cartridge a case containing multiple components including recordable tape ... QIC media for the 5.25-inch form factor is a data cartridge; QIC media for the 3.5-inch form factor is a minicartridge
coercivity the field strength required to change the magnetic state of magnetic material; expressed in Oersteds
compare to verify that a copy of a file is identical to the source
compression (data compression) an algorithm that reduces redundant strings of data, resulting in decreased file sizes; can be performed by hardware or software - but only one time
CRC (cyclic redundancy check) a complex mathematical method used to ensure the data written to the tape is error free data cartridge a QIC cartridge that can be used in 5.25-inch form factor drives
data density the measure of how much data is stored in a given length of tape or track ... typically expressed in BPI data encryption encoding data for maximum security
data integrity the validity of recorded information
data transfer rate the speed at which data is transferred between a host and a data recording device ... usually noted in bytes/sec or MB/minute
directory an area or data structure in which information is stored regarding the location and contents of files and/or file structures ... also called directory partition
ECC (error correction code) a mathematical algorithm used to detect and correct errors should they occur
edge seek a method of using the recording head to detect the edge of tape and then to reference the tracks from the edge of tape, thus ensuring accurate track positioning
embedded OS an operating system which is self-contained with hardware and software which forms a component of a larger system and which functions without human intervention
encoding a method whereby a group of data bits is translated into a group of recording bits
_ GCR (group code recording) a data encoding method often used on several classes of QIC drives ... the code combines high data density with relative ease of decoding
_ MFM (modified frequency modulation) a recording code used on floppy-interface QIC drives ... it is the most efficient self-clocking mode
_ RLL (run length limited) a family of codes used to encode data ... they have the feature that the number of sequential zero or one bits is limited to a certain value ... group code recording (GCR) is an RLL code
environmental tolerance ability of a device to withstand changes in surroundings (such as temperature, humidity, dust levels) and continue to perform as specified
EOD (end of data) location on tape after which no information is recorded
EOP (end of partition) on tapes which are partitioned into logical volumes, the EOP is treated as the End of Tape for that volume ... a volume has only one EOT but has as many EOPs as partitions ... see also "BOP"
EOT (end of tape) designated by a specific hole pattern on quarter-inch tape cartridge media
erase to remove previously written data
error loss of magnetic signal strength to a degree that data is uninterpretable
EW (early warning) a physical hole in the tape medium that indicates to the drive the EOT is approaching ... technically, the first hole in the EOT hole pattern ... this warning allows the drive to take the appropriate actions before reaching EOT
fast file access a method of locating and restoring files quickly ... also called rapid file access or quick file access
ferrite a ferromagnetic compound of ferric oxide used in the construction of magnetic recording heads and media
file one or more recorded blocks of data
file access time the amount of time it takes a tape drive to find a file
file-by-file backup and restore a method of backing up or restoring selected files in sets separately and sequentially
filemark an area of recording on tape used primarily to denote the beginning or end of a logical data structure, such as a file or set of files
_ setmark a tapemark that is hierarchically superior to a filemar
_ tapemark a unique data block used to separate data files or volumes of data
file recovery time file access time plus the time to transfer the file
file sort a sort of files by name
filler block a block containing no valid information in its data field ... the purpose of this block is to complete a frame in the event the host cannot fill the whole frame with valid data information
fixed blocks data organized into fixed-length "logical" blocks for transmission between devices ... see also "variable blocks"
flux transition a change in magnetic polarity in the tape media which, through a magnetic head and a tape drive's read circuitry, is translated into a data bit ... typically expressed in FRPI (flux reversals per inch) or FTPI (flux transitions per inch)
form factor the physical size of a device
_ full-height the same height as an equivalent full-height diskette drive
_ half-height the same height as an equivalent half-height diskette drive
_ third-height the front panel or bezel is approximately one-third the height of that specified for previous generations of similar devices which occupied the same horizontal space
format see "recording format"
frame a group of 64 blocks forming a complete logical unit
FRPI flux reversals per inch
FTPI flux transitions per inch
hard error permanent failed attempt to read or write data
hard error rate number of hard errors per bit
header a block of data written at the beginning of cartridges or files that contains specific identification information
HSM (hierarchical storage management) a system of ranking and storing information across a variety of device types
helical scan a method of reading and writing data to tape using a rotating head/drum assembly
initialize a process to prepare a data cartridge or minicartridge to read and write ... usually refers to retensioning the tape and header blocks prior to use
interchange removing a tape cartridge from one drive and reading the data on another driv
interface/tape drive interface the hardware and software used to establish communication between a host and a device
_ ATAPI (AT attachment packet interface) a command protocol used for accessing IDE peripheral devices
_ CDB (Command Descriptor Block) a command data block issued from a host to a target peripheral containing the operation to be performed and the parameters associated with that operation
_ floppy interface a physical interface between host computer and backup device enabled via a floppy disk controller
_ IDE (integrated device electronics) a standard communication interface which may be used between a host and a device
_ SCSI (small computer systems interface) a bus interface that enables many different kinds of devices, such as disk drives, CD-ROM drives and tape drives, to interface with the host computer
ISV (instantaneous speed variation) the fluctuation of speed of recording tape over extremely short periods of time
KB (kilobyte) a unit of measure for storage capacity: 1,000 bytes
LEW (logical early warning) an early warning point computed by the drive according to a vendor-unique algorithm
linear recording density the number of bits of data in a specific length of recording track ... see "BPI"
logical block groupings of organized data defined by system software for efficient transference between peripheral devices
logical file address a unique number, or address, is assigned to each logical data block for identification purposes ... these blocks are defined by the system software and are distinct from the physical blocks used by tape drives, or the sectors used by disk drives
logical format the arrangement of data on tape so that file and data structures are recognizable and recoverable by the host system
LP (load point) the physical location on the tape where data recording starts ... this location is physically marked by a punched hole
media a component used to store data such as a tape or rotating disk.
_ barium ferrite a magnetically retentive material used in recording media
_ ferric oxide a magnetically retentive material used in recording media
ME (metal evaporated) media with a film of metallic recording material deposited by an evaporative process
MP (metal particle) a type of media coated with metallic particles
migration path planned development direction of a product category
minicartridge a QIC cartridge that can be used in 3.5-inch form factor drives
MTBF (mean time between failure) expected drive life before first failure
multimedia edit a utility enabling modification, production or mastering of audio, graphics, text or video data and files in a professional production environment or desktop environment
multimedia playback a utility enabling presentation of audio, graphics, text or video data or files as real-time sound and visual events
multitasking the concurrent execution of several jobs
multithreading multiple concurrent threads of execution within a single application
native not compressed
near-line storage data not immediately accessible by the host but available without human intervention (e.g. data storage library system)
network compatibility the capability of hardware or software to operate in a multi-user, multi-system or multi-node configuration, as opposed to an individual stand-alone system
Oersted (Oe) the measurement of force required to produce a change in the magnetic state of media ... higher numbers equate with higher packing density and increased capacity ... see also "coercivity"
OS (operating system) creates a common platform and infrastructure for all software to operate and communicate with the PC and peripherals devices
off-line storage data which is accessed through human intervention (e.g. warehoused media)
operating temperature the upper and lower limits for running hardware as specified by the manufacturer
overrun/buffer overrun the condition occurring when the rate at which data is read from tape exceeds the rate at which the host system can transfer data from the tape drive controller ... when the buffer is full, the tape drive must stop reading, empty the buffer, reposition the read head with respect to the last data read, and resume reading ... this time consuming task reduces overall system data transfer ... see also "underrun" and "buffer"
overwrite a method of recording over data on a tape without erasing it
physical block address on all formatted QIC tapes, data is recorded in physical blocks which are numbered sequentially from the BOP and whose size is fixed by the recording format standard ... the number of each physical block is unique and may be used as an address to locate data
physical format the actual arrangement of binary information recorded on tape to enable the separation of data and tape drive control information ... QIC recording formats are specified in development standards
postamble a pattern of recorded data used to synchronize the data encoding electronics to the data stream ... it occurs at the end of the data block
preamble a pattern of recorded data used to synchronize the data encoding electronics to the data stream ... it occurs at the start of the data block
QFA (quick file access) a method of locating files quickly using high tape speeds
QIC Quarter-Inch Cartridge Drive Standards, Inc., an international trade association comprised of manufacturers of QIC tape drives, media and critical components ... its primary charters are to identify market needs; educate users, OEMs, system integrators, resellers and dealers; and provide a forum for technical discussions leading to the generation of development standards for compatibility among manufacturers' systems
QIC technology methods of storing and managing information using QIC drives and media
RAW (read after write) a method of ensuring that data written to tape is correct ... see also "RWW"
rapid file access see "fast file access"
read/write compatibility the ability to exchange recorded information
read/write head a device which uses induction to "write" a data pattern onto magnetic media; and which uses either inductance or magnetoresistance to "read" the data back ... heads come in many different shapes and forms, and are used for both contact and non-contact type recording
_ brass constructed of half hard brass and MuMetal or HyMu laminations,wound with very small gauge wire ... generally used for lower flux density recording ... can be either single or multi-channel, used mainly on QIC-40-MC and QIC-80-MC tape drives
_ ferrite constructed of a ceramic magnetic material, usually with either glass or chrome sputtered onto the gap area ... these generally are multi-channel heads, although some single channel designs have been built, mainly in use on QIC-80-MC and QIC-3010-MC tape drive
_ magnetoresistive thin film the various elements of the head structure are deposited with high precision on a substrate, enabling a more accurate head with narrower gaps; mainly used on QIC-3010/3020-MC drives
_ metal in gap (MIG) MIG heads have an Al-Fe alloy deposited on the interfacing pole pieces ... the bodies and cores of these types of heads are usually constructed of ferrite ceramics wound with the same type of wire as brass heads ... MIG heads allow for very high flux densities
read/write tape speed relative head-to-tape velocity during reading and writing
recording format the definition of how data is written to the tape ... it defines such things as the number and position of tracks, bits per inch and the recording code to be used
redirected restore retrieving information from a tape drive into a new logical area
reference burst a number of flux transitions written at the beginning of tape to indicate the center line of the tape ... this information allows the read head of the drive to align itself correctly and improves the data integrity of the drive
restore retrieving information from a tape drive and recording it on a disk drive
retension winding tape from one hub to the other to equalize tape tension ... new tapes and tapes that have been stored or used frequently should be retensioned before use
RWW (read while write) a method whereby data being recorded are read and verified on the same pass as they are written
scheduled backup backup routine performed at a predetermined time which typically involves taking over the host system; programmed by the software
search locating a data file
serpentine a bi-directional recording scheme; recording of one track in a forward direction is followed by recording the next track in a reverse direction
servo a closed-loop control system used to adjust head position and/or tape speed
servo burst a recorded signal used to control positioning
streamer a device that can transfer data with uninterrupted tape motion
streaming writing or reading blocks without stopping between blocks
tape catalog a listing of files stored on tape
tape rotation a method of backing up information on alternate groups of tapes to ensure an up-to-date copy of all files is on hand
TPI tracks per inchtracks/recording tracks the narrow strips of media on which data are written
transfer rate/data transfer rate the rate or speed at which information is written to tape, typically expressed in MB/minute or bytes/second
unattended backup backup automatically performed under software/system supervision without the need for human intervention
underrun (buffer underrun) the condition occurring when the rate at which the data written to tape exceeds the rate at which the host system can transfer data to the tape drive controller ... when the buffer is emptied, the tape drive must stop recording, refill the buffer, reposition the write head with respect to the last data written, and resume writing ... this time consuming task reduces overall system data transfer ... see also "overrun"
variable blocks data organized into variable-length logical blocks for transmission between devices ... no two blocks are necessarily the same size ...see also "fixed blocks"
versioning keeping a recording of each of a succession of versions, or revision levels, of a file or document
verify comparing data read to data written
volume a logical division of data
volume label a data block written at the front of a volume to identify it.