The expense of building and maintaining a secondary datacenter is one of the primary roadblocks for disaster recovery. Azure Site Recovery (ASR) is simple for any user to protect Azure applications and enable orchestrated recovery and health monitoring.

You can protect workload configurations which are currently supported by Azure. Azure has a fairly generous disk size limit of 1TB, which should suffice needs of common workloads, however, there are workloads that require larger volume sizes. In this blog, I describe how you can leverage Storage Spaces on Windows servers to configure larger disks and recover these VMs in Azure. An additional benefit of using Storage Spaces is the ability to get better storage IOPs for virtual disks carved out of Storage Spaces.

Until Azure starts natively supporting virtual machines with VHD sizes greater than 1TB, this solution can be used by customers who either need support for disks greater than 1TB, or want to take advantage of superior IOPs performance by creating volumes spanning multiple Azure disks using Storage Spaces.

Storage Spaces allows grouping of multiple disks into storage pools by then creating virtual disks from the available capacity in the storage pools. Refer to requirements under the Storage Spaces Overview section documentation for more details.

The example below depicts a customer who needs to protect a virtual machine ‘SalesVM1’ with a 3TB volume on a single disk name f1.vhdx. Remember, Virtual Machine and Cloud Service Sizes for Azure has a maximum limitation of 1TB for data disk. So, first we’ll need to create a single 3TB volume spanning three 1TB disks on the on-premises using Storage Spaces. Azure standard storage account has a per disk limit of 500IOPs but the application demands for 1500 IOPs for the disk, we also see how Storage Spaces help achieve the performance goal as well.

1. Create three new VHDXs (e.g.: ssdiskvhdx, ssdisk2.vhdx and ssdisk3.vhdx) with 1TB each.
2. Attach the three disks to the virtual machine ‘SalesVM1’.
3. Login into the virtual machine and set up a volume from Storage Spaces by following the steps below:
   • Bring the newly added disks online.
   • Create a storage pool.
   • Create a 3TB virtual disk out of the storage pool.
   • Initialize it as a single volume.
4. Copy the data from existing volume (based on vhdx) to new volume on virtual disk. It’s recommended that you stop any applications that operate on the old volume for the duration of the copy. This step is required if you have existing disks from which you need to copy the data. You can use command line tools like Robocopy for copying the data.
5. Wait for the copy to complete and then change the drive letter for existing 3TB volume, assign the same to newly created volume and start your applications.
6. To ensure the drive letters are preserved upon reboot set the SAN Policy to OnlineAll.
7. Detach the older 3TB virtual hard disk (vhdx) from the Hyper-V Manager Console.
8. Now that all the disks are under the 1TB limit, you can proceed with protecting the virtual machine to Azure using Azure Site Recovery.
9. Perform a Test Failover of the virtual machine to Azure and test the application.

Here are some key considerations before you decide to use Storage Spaces.

• Storage Spaces doesn’t support VSS based application-consistent snapshots.
  • ASR Hyper-V/VMM site protection scenario will allow only crash-consistent snapshots for VMs using Storage Spaces.
  • System Center DPM will allow only crash-consistent VM backup with Storage Spaces. For app-consistent backups, you can leverage in-guest DPM backups.
• VMware/Physical machine protection scenario doesn’t support VMs using Storage Spaces.
• Solutions relying on volume ID may be impacted as the data has been migrated to a new volume. For example, if you have an existing in-guest System Center DPM volume backup, you will need to re-protect the new volume.

If you have any feedback or features that you would like to see in ASR, send it our way using the Azure Site Recovery Feedback Forum.

Visit the Azure Site Recovery forum on MSDN for additional information and to engage with other customers. For more information, check out the Azure Site Recovery documentation.

Getting started with Azure Site Recovery is easy – all you need is to simply sign up for a free Microsoft Azure trial.