Hyper-V VMs on certain 20102/R2 hosts may crash after entering and leaving a save state due to a Microsoft defect in their January 2019 patch.
After January Microsoft Rollup patch KB4480963, Hyper-V VMs running on certain AMD-based hosts with Windows 2012 or 2012R2 will crash when attempting to leave a saved state.
The following error may be seen in Windows: "Failed to restore the virtual machine state: Cannot restore this virtual machine because the saved state data cannot be read. Delete the saved state data and then try to start the virtual machine. (0xC0370027)."
This issue does NOT impact Hyper-V 2016 or higher, and does NOT impact any Intel platforms or many older AMD platforms. See below for specific impacted platforms.
Microsoft does not have a resolution to this issue at this time of publication of this article. This is a confirmed Microsoft Issue impacting multiple backup vendors.
See the link below for release information from Microsoft and information on potential fix or workaround.Microsoft recommends after installing this update that any reboot of a host will require complete shutdown of VMs prior to powering off the host. Though not officially called out, this would also impact any other process that leverages VM save states, specifically including online backups that leverage Hyper-V Integration Services for online backups and potentially live motion operations.
Unitrends only option to continue to protect these systems impacted by Microsoft's defect is at this time to recommend agent installation in-guests on affected hosts and protect those systems using agent based protection, and discontinue host protection for affected hosts until the issue is confirmed resolved by Microsoft. Note depending on local architecture, this may only impact some Hyper-V hosts at a customer location. .
Customers may also be able to perform in-place upgrades to Hyper-V 2016 in some cases, or migrate VMs to other hosts or servers that are not impacted by this scenario to avoid the impact of this defect.
Per Microsoft This issue will impact Hyper-V hosts ONLY in the following configuration:
Windows 2012 or 2012R2 with Hyper-V role
Patch KB4480963 applied (Jan 2019 rollup)
Host runs on AMD Bulldozer Family 15h, AMD Jaguar Family 16h, or AMD Puma Family 16h (second generation) microarchitectures
In this configuration, when entering a save state and then later leaving a save state, the VM will fail to properly exit the save state which can result in VM crash in production, potentially resulting in data loss. Microsoft is planning to release a fix in a February 2019 update, but the initial update released did NOT include this fix.
Microsoft has confirmed this issue in the following KB: https://support.microsoft.com/en-us/help/4480963/windows-8-1-update-kb4480963
Note, switching from host-based to agent-based Unitrends protection will increase local and potentially cloud capacity for the Unitrends Appliance and may negatively impact backup appliance retention and should be done with care. Not all Unitrends UB license tiers include application support either so customers on free editions or essentials editions may need to perform other processes to protect database applications.