It can be, and that is a great solution for IT departments that currently have backup window problems. Disk resources are getting cheaper every day and SANs have technology that enable instant backup of massive data stores. By using the snapshot capabilities of high-end storage arrays, data can be backed up to disk in a matter of milliseconds.
This is by no means a replacement for tape based backups but CAN be used as such. Point-in-time copies of data can be taken at intervals during the day and be available for instant restore in case of corruption to primary volumes. If you plan to implement this as a replacement for tape backup, make sure your storage vendors snapshot technology uses RAID protected volumes for the image copies. This will protect the image if a drive failure occurs either during the image creation, or after the image is taken.
I usually do not recommend using disk-based backup as your only backup mechanism. Using snapshot image copies of production data that can be mounted in the SAN to a backup server provides zero impact LAN free backup. Use this technology in conjunction with tapes that can be taken off site. If you also replicate your data to a remote location for DR, then use snapshots on both sides to protect against rolling disasters. A snapshot at the primary side gives you instant recovery capability and the snapshot on the remote side will also protect you in case of corrupted production data being replicated to the remote site.
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This was first published in June 2002