Replication, Backup and Crackhead Mary

Last week I had a casual conversation with a guy about some basic concepts around replicated SANs and backups.  Dealing with virtualization and storage on a day to day basis it’s sometimes easy to forget that some people are not very familiar with the details of replicated SAN’s and disk based backup technologies.  So the question was posed, “if I have replicated SAN’s do I really need to spend money on backup?”.   The idea that “hey I’ve got two copies of the data at different sites. I should be good to go short of a nuclear bomb hitting the east coast.” is how many people look at backup/DR.

The idea that with replicated SAN’s, if one site becomes a smoking hole you still have the exact same data at another site (assuming sync replication) is certainly a true statement.  In a true “smoking hole” scenario this is probably what you want right?  All your data is there and, provided you have a solid failover process in place, you should be back up and running soon.  Let’s face it though, the smoking hole scenario, while horrible, is not as common as say the ID10T type of scenario that you probably deal with on a weekly or even daily basis.  When Mary from HR deletes the entire department directory one morning because she was out smokin’ crack and doing Jello shooters til 2 am that same morning – replicated SAN’s are simply going to replicate Mary’s stupidity to both sites.  Perhaps an even a worse senario is when your CEO asks you to recover a file he thinks he deleted 2 weeks ago – replicated SAN’s aren’t going to help you much here either, although there should be replicated copies of your termination papers at both sites real soon!

You can see where I’m going with this.  Now obviously with Snapshot technology and things like CDP and CRR technologies like RecoverPoint some of these ID10T error can be mitigated but there is still no real replacement for a good backup strategy.  Replication is great for DR where recovery times have to be very fast and data loss has to be kept to a minimum but unless it is used in conjuction with a solid backup strategy you are really only protecting yourself from the smoking hole scenario which, if we’re lucky, will never happen.  Crackhead Mary and delete-key happy executives are going to be problems you will deal with with much more regularity.

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