If deploying Windows Virtual Desktop, having the multiple redundant control plane that Azure provides is a very attractive proposition! If a Azure region fails, your WVD connection routes to another Azure region on the platform layer. Your end users shouldn’t notice a thing right?
However, what happens to your IaaS virtual machines that serves as your WVD session hosts and pools? Those aren’t protected. I will go over some scenarios you can setup to protect your environment from regional failures when running a Windows Virtual Desktop workload.
1) Active/Passive Setup – using FSLogix VHDx
In an active-passive setup, you have a single pool setup in a single region. You store your FSlogix profiles on the file server \\fs01\Profiles\%username%
You use a backup tool that copies permissions over to another file share, preferably on a different file server running your paired fail-over region. As for the replication intervals, I would suggest once every 4 hours. Remember, you will incur cross region bandwidth charges between the two vNet peers you are replicating to.
For example: If my primary Azure region where my Pool-A is located, Pool-B should ideally be located in Central US. In Central US would be my active fs02 server running a D2sv3 machine with Premium SSD’s.
When you spin up Pool-B, go to your image for Pool-B and setup your FSLogix registry settings to point the FSLogix VHD location to: \\fs02\Profiles\%%username%. Your FSLogix Redirected XML doucment should also be pointing to your \\fs02 folder path with the same XML document. Your Pool-B image should be identical to your Pool-A image except for that change.
When US East goes down, you immediately turn on Pool-B and re-assign all active WVD users to Pool-B and the last good copy of your FSLogix profile will already be synced with FS02 and your running WVD environment is ready to go.
You can use Azure Site Recovery for all other VM’s and LOB apps.
2) Active/Active Setup – using FSLogix CloudCache
In a Active-Active setup, we are going to use FSLogix CloudCache.
FSLogix CloudCache allows you to point a user profile to up to 4 providers. A provider is a location where you specify that will contain synced copies of every users VHD.
For example, provider 1 (primary) can be a SMB Share on a File Server in US East, provider 2 can be a Azure Files SMB path in US East, provider 3 can be in US Central on a File Server, and provider 4 can be in US Central in a Azure File share there.
You specify the paths of the providers in the same FSLogix registry settings but you cannot have both a VHD Location and CloudCache Location at the same time, it’s either one of the other.
In US East on Pool A, you can setup the providers pointing to the 4 provider locations in the order you wish to use as the primary. We can prioritize as such (ie: Provider 1 – Azure Files (US East) ; Provider 2- SMB Share on File Server (US East); Provider 3 – Azure Files (US Central); Provider 4 – SMB Share on File Server (US Central).
The great thing is that CloudCache manages all the failover and failback if a provider does go down. It will sync up automatically. On the WVD Session host itself, there is a Cache folder in C:\ProgramData\FSlogix\Cache that stores all the users cache files, make sure you have enough space on your C drive for that. You can specify a different path for this cache file but make sure its fast. The temporary drive in a VM is also a place to store this cache file temporarily, otherwise store them on a Premium disk.
Some drawbacks are that initially during first time logins, it takes additional time to cache to your local disk, and upon log off, it takes type to sync back to all 4 providers. The log off process won’t complete until all 4 providers have been synced up. Potential issues here is that you are going to likely run into IOPS issues on your disks. In a DR scenario, that should be acceptable for the average client.