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Veeam: Failed to prepare (Hyper-V) guests for volume snapshot

After a few big months (we recently moved back to the U.S. for a couple of years) – I thought I better get back to some blogging!  Here is a recent issue I’ve ran into for a customer while setting up a new Veeam environment to backup a Hyper-V cluster:

Host and guest O/S both Server 2012 R2.  When backing up a specific VM I received the following errors:

Unable to create snapshot (Microsoft CSV Shadow Copy Provider) (mode: Crash consistent). Details: Failed to prepare guests for volume snapshot.
Unable to create snapshot (Microsoft CSV Shadow Copy Provider) (mode: Crash consistent). Details: Failed to prepare guests for volume snapshot.
Processing servername Error: Failed to prepare guests for volume snapshot.


I checked the VSS Writers, etc. and confirmed they were all good.  Checked to ensure there was snapshot space available.  There was no need to upgrade the Integration services as suggested.  After doing a little further digging, I noticed that the Hyper-V integration services components were set to disabled in the Guest O/S.  This was in spite of the properties for the VM stating otherwise:


The fix was to set all of the services to manual (triggered start) & reboot the VM.


Once this was completed backup ran successfully!


Veeam: A VSS critical writer has failed

While deploying Veeam Backup & Replication recently for a customer, we came across the following error message while backing up a domain controller:

Unable to release guest. Error: Unfreeze error: [Backup job failed.
Cannot create a shadow copy of the volumes containing writer’s data.
A VSS critical writer has failed. Writer name: [NTDS]. Class ID: [{b2014c9e-8711-4c5c-a5a9-

3cf384484757}]. Instance ID: [{bcc3ddec-3a1b-4bbd-bb5c-2da62e9bcb4d}]. Writer’s state: [VSS_WS_FAILED_AT_POST_SNAPSHOT]. Error code: [0x800423f4].]

Running VSSAdmin List Writers showed in fact that the NTDS Writer was in an Error state with [11] Failed, “Non-retryable error”.

The issue was due to a conflict with Shadow Protect, which was also doing VSS Backups.  As Veeam was going to be replacing ShadowProtect, the fix for this was to remove the Shadow Protect VSS Provider:

First re-run the ShadowProtect backup which restored the NTDS Writer to a Ready State.

Open Regedit
Browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Providers\
You should see the GUID {24602736-bed9-4619-91b0-243447c6409c} listed.  Clicking on it shows “StorageCraft Volume Snapshot Software Provider”
Backup this registry key, then delete it.
Open Windows services and restart the “Volume Shadow Copy” service. It may be stopped to begin with, that’s okay.
Check and see if the provider is gone from: vssadmin list providers
Reboot the server when next possible.

Re-run Veeam backup and all should be successful!