Member Avatar for SyncMaster170

daniwebbers,

This is my issue. I need to back up one server, that has server 2008 r2 installed. It does have sql server 2008 installed, but I successfully back up our databases every day so that is not an issue. In the event viewer this is the error I am getting about backing up the server:

Backup started at 'DATERANGE' failed as Volume Shadow copy operation failed for backup volumes with following error code '2155348129'. Please rerun backup once issue is resolved.

I ran cmd as admin, typed vssadmin list writers, then hit enter.
This is what failed-
Writer Name- "Microsoft Hyper-v VSS Writer"
State- {8} Failed
Last error- Retryable Error

It has two hyper-v virtual machines on it, and both vm's have more than 5GB of available space on them, so the windows back up isnt failing because of a disk space issue.

But I critically need to do a backup asap. Any help would be much appreciated and I will credit responses with points. Thanks!

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Dani AI

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Short diagnosis and what this thread already shows: the Windows Backup event 521 with error code 2155348129 is a VSS/SPP failure — the shadow-copy request did not complete. When the Hyper‑V VSS writer reports a "Retryable Error" it usually means the host attempted an online snapshot but the snapshot process could not be completed (often because one or more guest-side writers or the integration path couldn’t quiesce the VM). (learn.microsoft.com)

Likely causes to investigate (quick checklist): stuck or failed VSS writers inside guest OSes, out-of-date Hyper‑V integration components, existing checkpoints/checkpoints merge activity, insufficient free space for the VSS storage area, or heavy I/O that causes VSS timeouts. Check both the host’s Hyper‑V/VMMS and the guest Application/System event logs for VSS errors and shadow-copy timeouts. (support.microsoft.com)

Practical remediation path: short term — the cheapest reliable option is exactly what used (shutdown or pause the VMs so the host backup can complete). Medium/long term — ensure guests’ VSS writers are healthy and updated, update Hyper‑V integration components and host patches, consolidate/delete stale checkpoints, and guarantee enough free space (vendors commonly recommend ~10–15% free on targets). For production consider guest‑agent backups or a Hyper‑V‑aware backup product that handles VSS coordination. ’s suggestion to reset/re‑register VSS components can clear stuck writers as a recovery step, but it’s not a substitute for finding the underlying cause. ()

Operational tips and cautions: don’t rely on one‑off hacks (some online “fixes” like toggling active partitions can break boot), and schedule an outage window to reproduce and capture detailed logs if the error persists. If you need to get a consistent backup immediately and can’t fix VSS quickly, export or cold‑shutdown the VMs and copy their VHD/VHDX files as a fallback. If the writer repeatedly fails after resets, gather the full VSS and VMMS event entries and escalate to your backup vendor or Microsoft support. (helpdesk.kaseya.com)

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Member Avatar for CimmerianX

Check to make sure you only have 1 vss writer on the server:
"vssadmin list writers"

Multiple writers sometimes cause issues.

You could try a full VSS reset:

net stop "System Event Notification Service"
net stop "Background Intelligent Transfer Service"
net stop "COM+ Event System"
net stop "Microsoft Software Shadow Copy Provider"
net stop "Volume Shadow Copy"
cd /d %windir%\system32
net stop vss
net stop swprv
regsvr32 /s ATL.DLL
regsvr32 /s comsvcs.DLL
regsvr32 /s credui.DLL
regsvr32 /s CRYPTNET.DLL
regsvr32 /s CRYPTUI.DLL
regsvr32 /s dhcpqec.DLL
regsvr32 /s dssenh.DLL
regsvr32 /s eapqec.DLL
regsvr32 /s esscli.DLL
regsvr32 /s FastProx.DLL
regsvr32 /s FirewallAPI.DLL
regsvr32 /s kmsvc.DLL
regsvr32 /s lsmproxy.DLL
regsvr32 /s MSCTF.DLL
regsvr32 /s msi.DLL
regsvr32 /s msxml3.DLL
regsvr32 /s ncprov.DLL
regsvr32 /s ole32.DLL
regsvr32 /s OLEACC.DLL
regsvr32 /s OLEAUT32.DLL
regsvr32 /s PROPSYS.DLL
regsvr32 /s QAgent.DLL
regsvr32 /s qagentrt.DLL
regsvr32 /s QUtil.DLL
regsvr32 /s raschap.DLL
regsvr32 /s RASQEC.DLL
regsvr32 /s rastls.DLL
regsvr32 /s repdrvfs.DLL
regsvr32 /s RPCRT4.DLL
regsvr32 /s rsaenh.DLL
regsvr32 /s SHELL32.DLL
regsvr32 /s shsvcs.DLL
regsvr32 /s /i swprv.DLL
regsvr32 /s tschannel.DLL
regsvr32 /s USERENV.DLL
regsvr32 /s vss_ps.DLL
regsvr32 /s wbemcons.DLL
regsvr32 /s wbemcore.DLL
regsvr32 /s wbemess.DLL
regsvr32 /s wbemsvc.DLL
regsvr32 /s WINHTTP.DLL
regsvr32 /s WINTRUST.DLL
regsvr32 /s wmiprvsd.DLL
regsvr32 /s wmisvc.DLL
regsvr32 /s wmiutils.DLL
regsvr32 /s wuaueng.DLL
sfc /SCANFILE=%windir%\system32\catsrv.DLL
sfc /SCANFILE=%windir%\system32\catsrvut.DLL
sfc /SCANFILE=%windir%\system32\CLBCatQ.DLL
net start "COM+ Event System"

Member Avatar for SyncMaster170

I just got done researching some more into the topic and got my vss writer to be stable again. When the time comes(4pm eastern today) I will be attempting to do another server backup and will report back. But to fix the vss writer error simply do the following steps:
1. On the keyboard, hold the windows key and press R.
2. type services.msc
3. Find Hyper-V Virtual Machine Management and restart the service(Dont worry this does not affect any running vm's)
4.open command prompt under admin priviledges and type vssadmin list writers.

The error should be gone and vss writer state should say Stable, with no errors.

Edited by SyncMaster170 because: typo
Member Avatar for SyncMaster170

So the issue lied within the vm's. I had to turn them off, then start the backup procedure, then turn them back on once the backup is complete.

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