A customer has the ability to use Locally Redundant Storage (LRS) to protect their data in the datacenter they choose or Geographically Redundant Storage (GRS) to protect them from a datacenter failure. Once Microsoft puts their failover into action. (The rule of thumb here is Microsoft deems that they cannot recover their datacenter in a timely manner. No SLA posted and they failover to another datacenter. We can see what datacenter they failover to here) For more details on Azure Storage Redundancy Options go (here).
So the question is, how does a Partner backup a customer’s VM? Today, they only way this can happen would be to create a snapshot of their blob storage (here). The other option would be to utilize the following scripting located (here) Backup and Restore Windows Azure IaaS virtual Machines using BLOB Snapshots. Installing Azure PowerShell details are located (here)
For more information on Azure Site Recovery – Click here (Premises to Cloud)