Look Up Another Term

Definition: magnetic tape


A sequential storage medium used for data collection, backup and archiving. The first electronic storage medium, magnetic tape is made of flexible plastic with one side coated with a ferromagnetic material. Tapes were originally open reels but were superseded by cartridges and cassettes of many sizes and shapes. Today, LTO is the only surviving tape technology. See LTO.

Tape has always been more economical than disks for archival data; however, disk capacities have increased enormously while the cost per bit has been reduced dramatically. In addition, if tapes are stored for the duration, they must be periodically recopied or the tightly coiled magnetic surfaces may contaminate each other.

Sequential Medium
The major drawback of tape is its sequential format. Locating a specific record requires reading every record in front of it or searching for markers that identify predefined partitions. Although tapes today are used for archiving rather than real-time updating, some drives allow rewriting in place if the byte count remains the same. Otherwise, updating requires reading the original tape, changing the data or inserting new records and rewriting everything onto another tape.

Track Formats
Data are recorded in blocks of contiguous bytes, separated by a space called an "interrecord gap" or "interblock gap." Drive speed is measured in inches per second (ips). Over the decades, storage density jumped from 200 bits per square inch to millions and billions of bits.




Tracks on Magnetic Tape
Except for helical scan, most tracks on tape run parallel to the length of the tape. See helical scan and serpentine recording.






An LTO Cartridge
Linear Tape Open is the only tape drive technology that continues to be manufactured. See LTO.




Old Tape Formats
The following tape drives are no longer manufactured, although media may still be found. In order to read these tapes, the appropriate tape drive must be available, and drivers for such hardware may not work in current operating systems.