Enterprise storage, planning and management
When to choose tape
By Rick Cook
Tape is still the major medium for backup, disaster recovery and archival storage. Growing choices and shrinking costs between competing products mean that storage administrators need to consider their options when designing a backup architecture.
Here are some of the situations where tape is a strong contender:
You have adequate time for backups.
One of the biggest problems with tape is that it is slow. This is less important if your backup window isn't closing down on you. Options like disk-to-disk-to-tape are one way to stabilize the window and still get the advantages of tape.
Quick recovery of files and directories isn't needed or can be handled by other means.
Any block-based storage system (which usually includes tape) is not ideal for getting individual files back quickly. That doesn't matter in some applications. In others, the need can be, alternates such as point-in-time snapshots or mirroring can be used to meet that need.
You need to store data offline in large chunks.
The latest generation of SDLT tapes can store up to 600 GB (compressed) on a single tape and Quantum is expected to introduce DLT-S4 tapes with 1.6 TB capacity (compressed) in the near future. This puts tape capacities well ahead of other removable data storage media.
You need long-life archival storage of large quantities of information.
Increasingly, enterprises are realizing there are differences between archival and backup storage. While tape is increasingly being challenged in the backup arena, it still excels at archival storage. Properly stored, tape has an expected life of at least 20 years.
You need off-site archival storage of large quantities of information.
Tapes are high capacity and portable. If your disaster recovery plan calls for moving data offsite for long term storage, the economics of tape are just about unbeatable.
You need a low-cost solution.
This isn't the no-brainer it once was, but tape is one of the cheapest ways to go for most backup and disaster recovery applications.
Finally, keep in mind that you have options. Tape is no longer the only choice for most of these jobs and you need to weigh the costs and other tradeoffs before settling on a storage medium.
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About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
21 Feb 2005
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