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].]
veeamerror

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.
veeamerror1

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”
veeamerror3
Backup this registry key, then delete it.
veeamerror2
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!

About AJ McKean

Based in sunny Tauranga, New Zealand, AJ McKean is a Senior Systems Engineer in Mt Maunganui. With over 15 years of professional IT experience working in both New Zealand and the United States, he holds several certifications including MCSE(2000-2003), MCITP:Enterprise(2008), MCSA(2012), VMware VCP-DCV5.5, CompTIA A+ & is an HP Storage Architect. He is passionate about all things IT, especially virtualization, automation & cloud technologies.

One response to “Veeam: A VSS critical writer has failed”

  1. Sean Perryman says :

    Thanks, this seems to have worked for me. Not the first time StorageCraft has thrown a wrench in the works.

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