A tape drive is a device that stores computer data on magnetic tape, especially for backup and archiving purposes. Like an ordinary tape recorder, a tape drive records data on a loop of flexible celluloid-like material that can be read and also erased. Tape drives work either by using a traditional helical scan where the recording and playback heads touch the tape, or linear tape technology, where the heads never actually touch the tape. Drives can be rewinding, where the device issues a rewind command at the end of a session, or non-rewinding. Rewinding devices are most commonly used when a tape is to be unmounted at the end of a session after batch processing of large amounts of data (payroll is the classic example). Non-rewinding devices are useful for incremental backups and other applications where new files are added to the end of the previous session's files.
A benefit of a tape drive backup is that tapes have a large capacity for storing data and are very economical when compared to the cost of hard disk storage. A disadvantage is that tape drives store data sequentially, and the user can only access specific data by starting at the beginning and rolling through the tape until the desired data is located.
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