Backup and restore are the cornerstones of data protection. They are the methods most used to protect critical data. The purpose of backing up data is to be able to recover it later. Backup consists of copying data to another place for safekeeping. Restore is the operation in which data is copied back to primary storage after data is lost or damaged. The most popular is magnetic tape, with disk-based backup becoming more common. Backup architectures include internal and external DAS systems, network-based or LAN-based backup, NAS backup with or without NDMP, and SAN backup. These architectures represent different levels of cost and performance. Backup software is also a critical component of backup systems. Depending on the architecture of the system, backup software may be a single program and process or a highly distributed server-based software system. Tape has the benefit of being well understood, reliable, high capacity, inexpensive, reusable, and removable. The disadvantages are that tapes break and are slow relative to disk systems. Disk-based systems are fast but more expensive. Disk-to-disk-to-tape backups extend the disk-based backup model to include the cloning of the backup image to a set of tapes. This provides for a removable backup set that can be taken off-site. Though archive also entails copying data to media, it is fundamentally different from backup. Archival data is not expected to be restored in a timely fashion and instead is expected to be stored away for long periods of time. Archive systems tend to be slower but have greater media longevity than backup systems.
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