Data deduplication or tape archive for reducing data on disk?

Data deduplication can reduce data stored on disk, but you'll probably need a tape archive for data with long retention requirements.

I use virtual tape backup with RAID 5 and was thinking of adding additional tape as an archiving target. Would you recommend using data deduplication to reduce the data on disk instead of a tape archive?

It's not an either/or choice between data deduplication and a tape archive. You should think of doing both.

Unless your backup retention policies dictate that you only need to keep backups for a few weeks, you are still likely to need a tape archive for long-term storage of important data, such as monthly or year-end data sets.

However, more and more clients I work with are considering retaining their daily and weekly backups (which typically only need to be kept for two to four weeks) on disk using data deduplication. This is particularly attractive if you can replicate the dedupe images between intelligent devices across data centres for disaster recovery (DR) purposes.

We can perform data deduplication in several different places nowadays. Just about all new virtual tape library (VTL) devices feature dedupe functionality, and backup software vendors are increasingly incorporating it into their backup applications (either at the client or at the backup server). You also have the option of data deduplication for primary storage with certain network-attached storage (NAS) solutions. Backup data deduplication solutions analyse and process the data stream between the backup server or client and the target storage device, eliminating duplicated data patterns before they are stored.

Data deduplication has the potential to reduce the size of backup disk volumes from 20% to 95%, but some careful analysis is needed at the scoping and sizing phases to ensure that your backup data will dedupe. Some image or file pre-compression utilities, for example, will create data sets which cannot be reduced in size and are not good candidates for data deduplication.

Depending on the age of your existing virtual tape library, it may be time to think about an upgrade or replacement to help make your backup life easier.

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