Ntbackup.exe supports backup to disk as well as to tape, and snapshots and cloning are two approaches to disk backups. You can take a snapshot in seconds rather than in hours (which tape-based backups of large databases often require). However, you need sufficient disk space to store the snapshot, which usually equals the size of the database that you back up. Also, Exchange 2000 Server doesn't offer native support for snapshots or clones.
A snapshot is a logical copy of a disk volume—think of it as a physical copy of the block map that maps a RAID volume's logical blocks to the physical blocks on the volume's disks. You can use the snapshot as a separate LU (and therefore as a separate Windows 2000 device) that points to the original physical disks. You can implement a block map at the OS or RAID-controller level.
Cloning, which other OSs have offered for well more than a decade, is a simple idea: Add a mirror member to a volume, let the OS update the member so that it contains the same content as the volume, then break the member out of the mirror set. The result—an exact physical copy of the volume—can contain one or more databases. If you lose the original database, you can swap in the cloned copy and replay the transaction logs to recover data, then bring the restored database online. . . .
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