This is an issue that effects quite a few people and numerous forum threads can be found on the internet by those searching for the solution.
This can occur both when taking manual snapshots of virtual machines when one chooses “Quiesce guest filesystem”, or when using snapshot based backup applications such as vSphere Data Protection (vSphere vDP).
For the last couple days, one of my test VMs (Windows Server 2012 R2) has been experiencing this issue and the snapshot has been failing with the following errors:
An error occurred while taking a snapshot: Failed to quiesce the virtual machine.
An error occurred while saving the snapshot: Failed to quiesce the virtual machine.
As always with standard troubleshooting, I restarted the VM, checked for VSS provider errors, and insured that the Windows Services involved with snapshots were in their correct state and configuration. Unfortunately this had no effect, and everything was configured the way it should be.
I also tried to re-install VMWare tools, which had no effect.
PLEASE NOTE: If you experience this issue, you should confirm the services are in their correct state and configuration, as outlined in VMware KB: 1007696. Source: https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1007696
The Surprise Fix:
In the days leading up to the failure when things were running properly, I did notice that the quiesced snapshots for that VM were taking a long time process, but were still functioning correctly before the failure.
This morning during troubleshooting, I went ahead and deleted all the Windows Volume Shadow Copies which are internal and inside of the Virtual Machine itself. These are the shadow copies that the Windows guest operating system takes on it’s own filesystem (completely unrelated to VMware).
To my surprise after doing this, not only was I able to create a quiesced snapshot, but the snapshot processed almost instantly (200x faster than previously when it was functioning).
I’m assuming this was causing a high load for the VMware snapshot to process and a timeout was being hit on snapshot creation which caused the issue. While Windows volume shadow copies are unrelated to VMware snapshots, they both utilize the same VSS (Volume Shadow Copy Service) system inside of windows to function and process. One must also keep in mind that the Windows volume shadow copies will of course be part of a VMware snapshot.
PLEASE NOTE: Deleting your Windows Volume Shadow copies will delete your Windows volume snapshots inside of the virtual machine. You will lose the ability to restore files and folders from previous volume shadow copy snapshots. Be aware of what this means and what you are doing before attempting this fix.