Microsoft's had to hurry out a fix for a problem that breaks live VM migration. And it's a problem Redmond brought upon itself with an Update Rollup to System Center 2016 Virtual Machine Manager.
Update Rollup 1 for that tool has the unintended side effect of making it impossible to migrate live VMs between different versions of Windows Server 2016 on different hosts.
When attempting live migrations, users are instead presented with the following error:
Unable to migrate or clone the virtual machine VM_name because the version of virtualization software on the host does not match the version of virtual machine's virtualization software on source version_number. To be migrated or cloned, the virtual machine must be stopped and should not contain any saved state.
Which is so not the point of live migrations, which are supposed to just happen.
Interestingly, the problem doesn't manifest when moving VMs between Windows Server 2016 and Windows Server 2012.
It's early days for Windows Server 2016 and production implementations will be few and far between, so not many will need to worry about this problem. Other than Microsoft, which surely isn't thrilled to have a glitch like this come along so soon after launch. ®