Magnetic Tape

Magnetic tape is a magnetic storage medium. The tape comes in a cartridge, and a tape drive reads data from it and writes data to it.

Very high capacity, very low cost per gigabyte

Magnetic tape holds a huge amount of data in one cartridge. It also has a very low cost per gigabyte, so storing each gigabyte costs very little. This makes tape cheap when you need to keep a large collection of files for a long time.

Sequential access is slow for one file

Magnetic tape uses sequential access. The drive must read the tape in order from the start, so to reach a file near the end it winds past everything before it. For example, a school radio club stores 500 recordings on one tape. To play recording 480, the drive must pass recordings 1 to 479 first, which takes time. Having lots of capacity does not make finding one file quick; the order is the reason access is slow.

Best for backup and archiving

Because tape is cheap for huge amounts of data but slow to search, it suits backing up or archiving large amounts of data that are rarely read back. A backup is a spare copy you can restore if the original is lost, and an archive is data you keep for the long term but hardly ever open. A local history society could copy thousands of scanned photographs and recordings onto tape and keep the cartridges safe for many years. Writing it all in one long run is cheap, and nobody needs to jump to one file quickly, so the slow search does not matter. Tape is a poor choice for files you are working on now, because you would wait for the drive to wind through the tape.