Tape Drives

The magnetic tape used in large computer systems is 0.5 inches wide and is mounted on a reel. The reel is placed in a special tape unit for use and the tape is automatically fed onto another reel. A tape of this type can store tens of gigabytes of data but it is likely to hold one file only. A file that is stored on tape must be sequential access and only the sequence that records are physically stored in is possible. This is because the tape is read from start to end and it would not be realistic to wind back and forth along the tape to find records in an out-of-sequence order.

Tape cartridges are a smaller form of magnetic tape. They are sealed units usually holding 0.25 inch tape and, like an audio cassette, both reels are built into the cartridge. Cartridges are used almost exclusively to hold backup-up copies of hard discs on small computer systems (a tape streamer). A cartridge can store up to about 20 gigabytes of data.

The school uses tapes to backup your data. Each night the data you saved on your P: drive is copied to a tape. The tapes are rotated to ensure that you should never loose data other than that which you are currently working on. Of course the system cannot overcome human error. If you forget to save your work or save it to the S: drive it will be lost!

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