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. The data are recorded as binary digits (bits) in the form of magnetized spots in one orientation or the other (0 or 1). See binary
Tapes were originally open reels but were superseded by a variety of cartridges and cassettes. Today, LTO is the only tape technology with future plans for increased storage capacities, although older tape systems are still in use. See LTO
and open reel
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.
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.
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. See magnetic tape formats
Tracks on Magnetic Tape