Tape drive
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A tape drive, also known as a streamer, is a data storage device that reads and writes data stored on a magnetic tape or a punched tape. It is typically used for archival storage of data stored on hard drives. Tape media generally has a favorable unit cost and long archival stability.
Instead of allowing random-access to data as hard disk drives do, tape drives only allow for sequential-access of data. A hard disk drive can move its read/write heads to any random part of the disk platters in a very short amount of time, but a tape drive must spend a considerable amount of time winding tape between reels to read any one particular piece of data. As a result, tape drives have very slow average seek times. Despite the slow seek time, tapes drives can stream data to tape very quickly. For example, modern LTO drives can reach continuous data transfer rates of up to 80 MB/s, which is as fast as most 10,000 rpm hard disks.
Tape drives can be connected to a computer with SCSI (most common), Fibre Channel, parallel port, IDE, USB, FireWire or other interfaces. Tape drives can range in capacity from a few megabytes to upwards of 800 GB. Tape drive storage is usually referred to with the assumption of 2:1, so a tape drive might be known as 80/160, meaning that the standard storage capacity is 80 whilst the compressed storage capacity can be up to 160 with compression. The raw storage capacity is known as the native capacity.
Tape drives can be found inside autoloaders and tape libraries which assist in loading, unloading and storing tapes.
In the 1980s some forms of tape drives were used as inexpensive alternatives to disk drives, examples include the ZX Microdrive and Rotronics Wafadrive.
[edit] Shoe-shining effect
The shoe-shining effect occurs during a tape backup process when the transfer rate of the data falls below the transfer speed of the tape drive. When this occurs, the data buffer of the tape drive empties and the drive must stop, reverse position and begin writing once the tape buffer fills again.
Shoe-shining can significantly affect the attainable backup speed and place undue stress on the tape medium itself.
[edit] See also
| Magnetic tape data storage formats | ||
|---|---|---|
| Linear | Helical-Scan | |
| Three Quarter Inch (~19 mm) | ||
| Half Inch (12.65 mm) |
UNISERVO (1951) - IBM 7 Track (1952) - IBM 9 Track (1964) - IBM 3480 (1984) - DLT (1984) - IBM 3590 (1995) - T9840 (1998) - T9940 (2000) - LTO Ultrium (2000) - T10000 (2006) |
Redwood SD-3 (1995) - DTF (19xx) - SAIT (2003) |
| Eight Millimeter (8 mm) |
Travan (1995) - IBM 3570 MP (1997) | |
| Quarter Inch (6.35 mm) | ||
| Four Millimeter (3.8 mm) |
DDS/DAT (1989) | |
| One Eighth Inch (3.18 mm) |
KC Standard, Compact Cassette (1975) - Datassette (1977) | |
| Stringy (1.58 - 1.9 mm) |
Exatron Stringy Floppy (1979) - ZX Microdrive (1983) - Rotronics Wafadrive (1984) | |
[edit] References
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.de:Bandlaufwerk pl:Napęd taśmowy ru:Стример fi:Kasettiasema zh:磁带机
