SQL Database Protection Using EMC RecoverPoint and EMC Replication Manager

A few times this week, questions have come up around the use of RecoverPoint for protecting SQL databases or really any databases.  The main questions are, “What all do I need?” and “How what exactly does the process look like?”

RecoverPoint is a cutting edge technology that enables you to provide continuous data protection (CDP) to your applications.  This is done though a process of journaling every write that is made.  The benefit of this is that you can then dial back to just about anypoint in time (given enough journal disk space) in the recent history of the data.  Another way to think of this would be “unlimited snapshots” or the personal favorite of account executives, “it’s Tivo for the datacenter!”.  Consider a situation where you have replicated arrays, Production and DR.  Data replication is being controlled by RecoverPoint and you have enough journal space to cover 2 days worth of changes to the data.  A SQL database is one of the application protected by RecoverPoint.  Lets say you have database corruption at 1pm but don’t realize it until 2pm.  Without RecoverPoint you’d be up the creek because now both of your replicated arrays have identical corrupted data and you’d have to go back to the last good backup to recover.  With RecoverPoint you could dial back to 12:59pm and recover from right before the corruption……..or could you?

The real answer is the resounding “it depends” BS we all hear so often.  In this case “it depends” on……well…….luck.  If you’re lucky, and there is a high chance you will be, you could simply roll back and recover from 12:59pm and keep your job.  The problem with RecoverPoint in a SQL environment is that it provides a crash consistent point from which to recover from.  If you’re not familiar with the term crash consistent, simply think of it as a dirty shut down of the SQL server.  There is a chance that there could be problems with recovering from one of these crash consistent points. So what do we do to get around this?  This is where EMC Replication Manager (RM) provides value.

Among other things, RM will allow you to take application consistent snapshots or in the case of RecoverPoint, to make application consistent bookmarks within RecoverPoint. Application consistency is achieved using Microsoft VSS within the SQL server.  These bookmarks need to be scheduled, say every 30 minutes or every hour or couple of hours.  So you may be thinking, hey that’s great, but what’s the point of spending all that money on RecoverPoint to have unlimited snaps if I’m now restricted to every 30 minutes or every hour?  Good question and this goes back to the “luck” I mentioned earlier.  There is a very good chance that you WILL be able to recover from one of the crash consistent points in time but no real guarantee.  If we’re talking about a tier 1 application, “maybe” and “I think so” are not the answers you want to be giving your boss when he asks “can we recover our SQL database”?.  Replication Manager generated, application consistent bookmarks give you a safety net and a guaranteed recovery point buy quiessing the database with VSS.

So, the process to recover from our previous example of the 1pm data corruption and assuming we were doing RM bookmarks ever 30 minutes, would look something like:

  • Attempt to recover from the last know good point in time, 12:59pm lets say.
  • If the recovery is good – Weeeeeee!  Now go back to playing Frogger at your desk.
  • If the recovery is bad either try another point in time or go back to 12:30pm when the last application consistent copy was made. Then go back to Frogger!

Another interesting thing to note:

As you would expect Replication Manager cost money.  I know, hard to believe EMC would actually charge you for something, but it is what it is.  What I didn’t realize until lately is that there are tools/utilities that are part of RecoverPoint product, including sqlsnap and sqlrestore, that will  provide application consistent SQL replicas but implementation is via user developed scripts.  So if you’re somewhat script savy and don’t mind managing things this way, there’s a FREE way out for you.

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