I'm trying to setup anti affinity with a cluster Hyper-V setup but am struggling to get any VMs to stay apart. It seems to be that the anti affinity is simply not honored.
Setup:
Attempt 1: I ran the below script on server1:
$WEBAntiAffinity = New-Object System.Collections.Specialized.StringCollection
$WEBAntiAffinity.Add("WEB Servers")
(Get-ClusterGroup –Name WEB_TEST_1).AntiAffinityClassNames = $WEBAntiAffinity
(Get-ClusterGroup –Name WEB_TEST_2).AntiAffinityClassNames = $WEBAntiAffinity
(Get-ClusterGroup –Name WEB_TEST_3).AntiAffinityClassNames = $WEBAntiAffinity
Get-ClusterGroup |Select-Object -Property name,AntiAffinityClassNames
All three VMs were powered off before I ran the above and all created on server1.
When powering them on, they all powered on and stayed on server1.
Attempt 2: I ran the same script above, on the additional servers (server2 and server3).
I powered off the VMs and powered them back on again, they again all remained on server1.
Attempt 3: After having ran the script on all the servers, I restarted the servers one by one. The VMs moved between nodes as normal during the reboots but when all were rebooted I stopped all the VMs, moved them to server1 and then started them again.
My assumption was that 2 would move before powering on but that didn't happen, they all started on server1.
Anyone know what I'm doing wrong here? Am I missing some pre-reqs? There's not a great amount of examples online that I've been able to find.
This is not called out specifically in Microsoft's documentation, but to make anti-affinity rules work in Hyper-V you also need System Center Virtual Machine Manager (SCVMM). SCVMM reads the anti-affinity rules (and other rules such as affinity, priority, etc.) and performs the migrations to apply those rules.
This is equivalent to the vmware stack, where ESXi is the hypervisor, the VM configuration contains the rules, and Director or vSphere actually apply the rules.