The first step and the most time-consuming part of inexpensive data pruning is setting the criteria for what you want to prune and what you want to do with it.
Also, as is usually the case with anything directly affecting your end users, there's a certain amount of social engineering involved in making changes and seeking input is an important way to build consensus.
Once you've quantified the kinds of data you're dealing with and their uses, you can start cutting the size of your backups. Here are several free and easy things you can do right now to reduce your backup windows.
Eliminate the obvious
A good deal of what is saved to disk doesn't need to be backed up at all. Things like temp files and internet caches seldom need to be backed up. This may amount to less than a gigabyte per user, but the size adds up and it's easy to automatically eliminate file types from your backup.
Get rid of non-business files
Video files need to be watched very closely. If there's no business reason for having avi files or YouTube videos, then don't back them up.
Use single-instance storage
Many modern backup programs allow you to store multiple instances of a document just once. This is especially useful for attachments, which tend to be large and have multiple copies within the organization. Most of the major backup vendors have products that support data deduplication.
Establish reasonable retention policies
Don't keep stuff you don't need. While some data must be retained for compliance regulations or company policy, most data has a definite lifespan. Once a file ages beyond usefulness it should be eliminated from storage, or at the very least not backed up any more.
Emails are a particular problem because most users turn their mailboxes into filing cabinets, saving messages for a year or more. It is safer and more efficient to require that email be moved to another directory after, say, 90 days. Why is this safer? Because email applications are archiving and they were never intended to be. They're not designed or structured for long-term retention and it can be hard to recover a specific message from an email "archive" in the event of a crash.
Archive your data
According to a ClearPath Solutions Group study approximately one-third of the data being stored by a typical company hasn't been accessed in 180 days or more. That data may need to be retained (or maybe not, see previous point), but it probably shouldn't have to be backed up regularly. By transferring the data to an archive, it can be saved once and eliminated from the regular backups.
Setting policies: Cutting your coat to fit your cloth
In setting backup policies it's important to match your goals to your resources. That is, if you are seriously constrained on your backups, you need more rigid policies on retention, time periods and such. When setting policies be sure to allow for expected growth in backup size, even with the new policies in place, and adjust your quotas and such as needed.
About the author: Rick Cook specializes in writing about issues related to storage and storage management.
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This was first published in December 2008