Tape storage. Tape storage is used primarily for backup and archival data.
Although magnetic tape is cheaper than disks, access to data is much slower,
because the tape must be accessed sequentially from the beginning. For this
reason, tape storage is referred to as sequential-access storage. In contrast,
disk storage is referred to as direct-access storage because it is possible to
read data from any location on disk.
Tapes have a high capacity (40- to 300-gigabyte tapes are currently available),
and can be removed from the tape drive, so they are well suited to
cheap archival storage. Tape libraries (jukeboxes) are used to hold exceptionally
large collections of data such as data from satellites,which could include
as much as hundreds of terabytes (1 terabyte = 1012 bytes), or even multiple
petabytes (1 petabyte = 1015 bytes) of data in a few cases.