Ask the Expert

Can replication and CDP replace a traditional backup regime?

My firm currently has one site and runs traditional backup with weekly fulls and nightly incrementals. We are planning to set up a second site as a DR site. Should we stick with traditional backups or is replication and CDP a way of replacing the existing backup regime?

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Replication seems like an easy way to overcome backup difficulties, however some SAN users have experienced a distinct downside to this approach. Replication is exactly that, whether offset or in real time, data is mirrored to a separate environment which means that the deletion or corruption of important files is also replicated. This can result in a disaster recovery (DR) environment which is of no use for data restore as it also contains said problem files. In order to overcome this it is possible on most SANs to retain previous snapshots of live data if the capacity is available.

I would certainly not personally abandon traditional backup methods completely, but look to create a mixed policy which still utilised tape for point-in-time backups and the replication function of the SAN to handle incremental backup tasks. This way you can effectively trash your incremental backup snapshots once you have verified your full tape job and begin the process again – this should ensure the DR SAN does not become overloaded with obsolete snapshots.

Also, if you then experience data corruption which is replicated, or total hardware loss (eg, in a fire) it will be possible to do a full restore from your tapes, therefore giving an effective worst-case scenario get-out-of-jail-free card.

This was first published in July 2009

 

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