How to Price Azure Backup

Safe backupAzure Backup is a great feature for simple disaster recovery to the cloud.  As with many of the Azure services, it improved and can now retain backups for a silly 99 years.  The pricing model originally depended on the total storage that was backed up but it was a lot more expensive than simple Azure storage and that made long-term retention uneconomical.  Pricing changed in April to reflect a more logical, but harder to understand, model.

Azure Backup differs from Azure Storage because it’s a service which includes bandwidth for transferring the data, the backup agent, compression and encryption.  You could simply run an on-site backup and copy up the backup files to Azure storage but you would not have encryption, you would need to manually perform the upload to cloud and if you wanted to restore any files, you might incur bandwidth charges.

The Azure pricing calculator is rather confusing but essentially when pricing Azure Backup you have the following two steps:

First, determine what you are protecting and how large each instance is.  You might be protecting a Virtual machine (this could be on-premises Hyper-V or an Azure virtual machine, Windows or Linux).  You might be protecting a Windows Server (perhaps running a server application or just a file server).  Finally, you might be protecting a Windows client machine as we blogged about previously.  Note that instances should all be 64-bit and some workloads, especially application servers like SQL Server or Exchange, will require System Center Data Protection Manager.

How to calculate Azure backup cost

Small and medium are pretty easy to calculate.  If you have large instances, you will be paying £6.109 (prices as of May 2015) per 500GB so a 1.3TB backup would cost you £18.33 per month.  A simple protection estate could be:

Instance Size Cost
 Windows Server 300GB £6.109
 Windows 7 laptop  45GB £3.0545
 Linux virtual machine 30GB £3.0545

And the cost for those would be £12.22 per month.  So that takes care of the backup service; the agent, compression, encryption and bandwidth.

Next we need to calculate the cost of the storage.  Microsoft have wisely brought this in line with the standard Azure Storage costs and you have the choice of locally redundant where your backup files are replicated three time within a single datacentre (e.g. Dublin) or zone redundant where they are replicated three times in one data centre and then three times in geographically paired datacentre (e.g. Dublin and Amsterdam).

How to calculate Azure backup cost


We’ve put a typical price per GB in the table above.  The actual figures vary with the amount of data you store and you can view current prices on the Azure Storage Prices.  Determining the amount of storage is a bit of a guessing game as it depends on how much the data changes (the churn), how many restore points you want to keep and the level of compression that can be achieved.  A file server with lots of Word documents will be compressed far more than a file server containing hundreds of .jpg images because the jpeg format is already compressed.  Azure will only charge for the actual storage used so your estimate doesn’t need to be accurate.  In our example, we might use the following factors:

1- the total storage of 375GB

2 – locally redundant storage because we only want an archiving and backup solution to replace tape-drives

3 – 20% of the data changes between backups

4 – 10% compression (this is conservative; a typical compression should be around 30-40% depending on the type of data being backed up)

5 – a backup every week

6 – retention period for the backups of 1 year (for a maximum of 52 backups stored after a year)

Our back-of-a-napkin calculation would be 375GB initial backup + 52 further backups would just be the data changes at 75GB (20% of 375GB).  Total of 4.275TB, with compression at 10% this comes down to 3.8475TB.

So after 1 year (at which point we will have a rolling 52 backups retained), our monthly cost might be £53.87 (for storage at a rough £0.014 per GB) + £12.22 (for the protected instances) = £66.09

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