SQL Azure – Disaster Recovery

In this post I look at how to set up some tooling to help implement a Disaster Recovery plan for your SQL Azure database.

Fundamentals

The key to any successful DR plan is that it has to be a fire and forget process.  If your DR process involves any manual components – ie Bob from infrastructure needs to push a button at 3pm on Wednesdays, you can guarantee that when disaster strikes you’ll discover Bob hasn’t pushed the button since February.

Thus you want to make sure everything is automated, and you want to hear about it if anything goes wrong.

It’s worth pointing out that every SQL Azure instance is mirrored twice, therefore it is highly unlikely you’re going to suffer an actual outage or data loss from unexpected downtime.  So what we’re doing here is creating a backup in-case someone inadvertently deletes the Customers table.  Of course it never hurts to have a backup under your pillow (so to speak) if it’s going to help you get to sleep at night.

Tooling

Tools you will need:

Exporting your SQL Azure DB

The first thing we’re going to do is to export your SQL Azure DB to a blob file.  The blob file can be used to import your backup into a new DB in the event of disaster.

  • If you haven’t already got one, create a new Azure Storage account.  It’s a good idea to create this in a different location from your SQL Azure DB, so in the event of a catastropic data-centre melt-down your backup will be located far away.  Eg if your database is in North-Europe setup your Storage Account in East-Asia.
  • Now fire-up Azure Storage Explorer and connect to your new storage account.  Create a new private container for sticking the backups in.  If you don’t create a container you can’t actually save anything into your storage account

  • Now we can configure Azure Import Export Client to download your DB into your newly created storage account.  This is a command line util which is ideal for automating but for now we’ll just run manually.  Run the following, editing for your specific account details:

  • Important – Make sure you the BLOBURL argument correctly specifies your container name, ie -BLOBURL http://iainsbackups.blob.core.windows.net/dbbackups/MyDb_120820.bacpac
  • If all has gone well you want to see something like below.  Note – this command simply kicks off the backup process it may take some time before your backup file is complete, you can actually monitor the backup jobs on the portal if you want.

Importing your SQL Azure DB

A DR plan is of little use if you don’t test your backup, so we want to ensure that our backup file can actually be used to create a rescue DB from.  So lets import our .bacpac file to see if we can recreate our DB and connect our app to it.

  • We basically reverse the process.  This time create a new empty SQL Azure DB
  • Now we can configure Azure Import Export Service to import our .bacpac file as follows:

  • If it works as expected we should see

  • Now you want to connect your app to your DB to ensure it works as expected.

Automating your backups

Now we’ve proven we can export and import our db we want to make sure the process happens automatically so we can forget about it.  The easiest way of doing that is to create a simple powershell script that runs the above commands for us, and then schedule it on the task manager.

Here’s a basic script that will run the Import/Export service for us, you can tailor as you see fit.  Note that I’m creating a timestamped backup file so we should get a new file every day

Now we have the script we can call it from the task scheduler, I created a Basic Task to run every night at 23:30, to call our script we can just run powershell from the schedular, as so:

Important – You will have to set your powershell executionpolicy to Remotesigned or the script won’t run when called.

Next Steps

So that’s it we’re backing up our Azure DB and storing in Blob storage all for the cost of a few pennies.  Next we might want to create a more sophisticated script/program that would email us in event of failure, or tidy up old backups – I’ll leave it up to you 🙂

Useful Links

http://msdn.microsoft.com/en-us/library/windowsazure/383f0cb9-0647-4e67-985d-e88369ef0508