Troubleshooting VSS (Volume Shadow Service) errors

📝 ​Disclaimer
The steps outlined in this article should be carried out only after consulting your System Administrator. As VSS is an operating system component, it is recommended to consult Microsoft or your System Administrator before proceeding.

Volume Shadow Copy Service (VSS) is a Windows component that Druva inSync uses to create consistent point-in-time snapshots of files — including open and in-use files — during backup. When VSS fails, the inSync backup either fails outright or falls back to reading the live volume directly, which can produce inconsistent backups of open files.

This article covers the most common VSS error codes returned during Druva inSync backup and restore operations on Windows endpoints and servers. It is written for IT administrators.

Before you begin, make sure you have:

Supported scope: Windows 10, Windows 11, and Windows Server 2016 or later.

Run these four checks first. They cover the most common root causes and resolve many VSS issues without needing error-code-specific steps.

Open an elevated Command Prompt and run:

vssadmin list writers

Every writer should report State: [1] Stable with no errors or warnings. A failed or timed-out writer is frequently the root cause of a backup failure.

vssadmin list providers
​

You should see only Microsoft Software Shadow Copy provider 1.0. Any third-party provider listed here may be interfering with snapshot creation.

Press Win + R, type services.msc, and press Enter. Confirm the following:

COM+ Event System

Microsoft Software Shadow Copy Provider

Volume Shadow Copy

Open Event Viewer (eventvwr.msc) and check the Application and System logs. Filter by Source: VSS to find detailed messages logged around the time of the backup failure.

Several errors in this article are resolved by re-registering the VSS system dynamic link libraries (DLLs). Run the following commands from an elevated Command Prompt:

cd /d %windir%\system32

net stop vss

net stop swprv

regsvr32 /s ole32.dll

regsvr32 /s oleaut32.dll

regsvr32 /s vss_ps.dll

vssvc /register

regsvr32 /s /i swprv.dll

regsvr32 /s /i eventcls.dll

regsvr32 /s es.dll

regsvr32 /s stdprov.dll

regsvr32 /s vssui.dll

regsvr32 /s msxml3.dll

net start vss

📝 Notes

The backup fails because VSS cannot create a snapshot. The inSync Client log records:

0x8000ffff [Catastrophic failure]. Continuing with actual volume...

📝 If the issue persists, see Troubleshooting VSS error 0x8000ffff while running inSync backup.

The backup fails because VSS cannot find a registered provider. The inSync Client log records:

0x80042304: The volume shadow copy provider is not registered in the system.

VSS DLL files are corrupted or unregistered.

Follow the steps in Re-registering VSS DLLs, then retry the inSync backup.

A VSS provider is blocking snapshot creation and the inSync backup fails. The cause is usually a third-party VSS provider conflict, corrupted DLLs, or a destination volume that is not formatted as NTFS.

Work through these checks in order.

1. Check for third-party VSS providers

vssadmin list providers

If any provider other than Microsoft Software Shadow Copy provider 1.0 is listed, consider uninstalling it — third-party providers are a common cause of this error. If the command hangs, a recently installed VSS provider is likely malfunctioning; uninstall it.
​

2. Check for concurrent backups

Confirm that the inSync backup is not running at the same time as another backup tool. Some providers permit only one snapshot at a time.
​

3. Check the disk for errors

chkdsk C: /f
​

4. Check the VSS registry setup state

If Windows is mid-setup or mid-upgrade, VSS is blocked. Open Registry Editor (regedit) and navigate to:
​

HKEY_LOCAL_MACHINE\SYSTEM\Setup

Confirm that SystemSetupInProgress and UpgradeInProgress are both set to 0.

​5. Re-register the VSS DLLs

Follow the steps in Re-registering VSS DLLs.
​

6. Verify that the destination drive uses NTFS

VSS requires the destination drive to be formatted as New Technology File System (NTFS). Confirm this in File Explorer or Disk Management.
​
​

The backup cannot process open or in-use files because VSS cannot locate the required snapshot object.

A VSS component — a service or a writer — that the backup depends on is unavailable or is not correctly registered.

net stop vss

net stop swprv

2. Follow the steps in Re-registering VSS DLLs.

3. Restart the machine.

4. After the restart, run vssadmin list writers and confirm all writers show State: [1] Stable with no errors.

5. Retry the inSync backup.
​
​

The backup fails because VSS cannot shadow copy the specified volume. This appears most often on cluster shared volumes or when a required VSS service is disabled.

The Microsoft Software Shadow Copy Provider service or the Volume Shadow Copy service is disabled or is not starting correctly.

What this means for your inSync backup

These errors indicate that Windows Volume Shadow Copy Service (VSS) could not add a volume to the shadow-copy set because a VSS limit was reached.

The applicable limit can vary depending on the Windows configuration, VSS provider, and shadow-copy feature in use. Therefore, this issue should not always be described as a fixed limit of 64 shadow copies per volume.
​

Cause

For error 0x80042317, the affected volume may have accumulated shadow copies or active shadow-copy-set associations that prevent VSS from adding it to another snapshot set.

For error 0x80042312, the backup request may be attempting to include more volumes in a single snapshot set than the VSS provider supports. Deleting shadow copies from an individual volume may not resolve this error if the snapshot set itself contains too many volumes.

Step 1: List the existing shadow copies

Run the following command from an elevated Command Prompt:

vssadmin list shadows /For=C:

Replace C: with the volume affected by the backup failure.

Step 2: Delete the oldest shadow copy

vssadmin delete shadows /For=C: /Oldest

Confirm the deletion when prompted, and then retry the inSync backup.

Repeat this step only when necessary.
​

Step 3: Delete all shadow copies for the affected volume

Use this option only when deleting the oldest shadow copy does not resolve the issue and the existing shadow copies are no longer required:

vssadmin delete shadows /For=C: /All /Quiet

The vssadmin delete shadows command can delete only client-accessible shadow copies. If Windows reports that the snapshots are outside the allowed context, they may need to be reviewed or removed using diskshadow or the application that created them.

Review how many volumes are being included in the same backup or VSS snapshot operation.

Where possible:

Deleting existing shadow copies may not resolve 0x80042312 because this error concerns the number of volumes included in a single shadow-copy set rather than the number of existing shadow copies on a volume.
​

Warning

Deleting shadow copies permanently removes the corresponding Windows restore points and Previous Versions data for the selected volume.

Before deleting any shadow copies:

Avoid running an unscoped deletion operation, as it may remove shadow copies from volumes other than the one affected by the backup issue.

VSS could not flush data to the volume in time to create the snapshot. The inSync backup fails or falls back to a live-volume backup.
​

High disk input/output (I/O) activity prevents VSS from completing the snapshot within the default time window.
​

chkdsk C: /f /r

4. After CHKDSK completes, run vssadmin list writers and confirm all writers show State: [1] Stable.

5. If the error persists, contact Druva Support — the VSS timeout threshold may need to be adjusted in the registry.

VSS encountered a problem while sending events to its writers. This is typically transient: the system could not hold I/O writes for the duration of the snapshot window.

The backup fails because VSS cannot communicate with one or more writers. Either the VSS service has stopped, or a specific writer — for example the SQL Server VSS Writer, Registry Writer, or System Writer — has failed.

The VSS service or an individual VSS writer is not running or has entered an error state. This also occurs when the VSS writer infrastructure fails to initialize.

net stop vss

net start vss

3. If a specific writer is failing, restart the Windows service associated with that writer.

4. Check Event Viewer for VSS errors in the Application and System logs around the time of the failure.

5. Retry the inSync backup.
​
​

VSS is already busy, either with a concurrent backup job or with a previous VSS process that did not terminate cleanly. inSync cannot start a new snapshot.

vssadmin list shadows

3. Delete stale shadow copies for the affected volume:

vssadmin delete shadows /For=C: /All /Quiet
​

⚠️ Warning: This removes all Windows restore points and Previous Versions data for the specified volume. Scope the command with /For= — omitting it deletes shadow copies on every volume.

4. Restart the VSS service:

net stop vss

net start vss

5. If the issue persists, restart the machine. This reliably clears stuck VSS processes.

6. If the error continues after the restart, follow the steps in Re-registering VSS DLLs.

A VSS writer failed to respond during snapshot creation. The writer may have crashed or become unresponsive. This is more common on systems with sustained high disk activity or heavily fragmented volumes.

VSS encountered an unexpected error while processing the backup operation. The inSync Client log may record:

The shadow copy provider had an unexpected error while trying to process the specified operation.

VSS system files are not registered, or the Microsoft Software Shadow Copy Provider service is not running.

VSS returned a bad state error, typically when a snapshot request includes remote components but no local components. The backup cannot create a snapshot.

The backup components object is not initialized correctly, or the VSS application programming interface (API) was called out of sequence.

VSS writers timed out during a lengthy shadow copy operation, causing the revert to fail and the volume to drop out of the snapshot set.

This usually occurs on machines with slow disks, limited memory, or a disabled disk write cache, where VSS writers cannot complete their work within the timeout window.

VSS attempted to import transportable hardware snapshots, but some failed because the import did not complete within the timeout window.

VSS timed out waiting for logical unit numbers (LUNs) to come online. This can happen when a hardware array is approaching the shadow copy limit.

The VSS import operation failed completely. No shadow copies were imported.

The affected volume spans multiple partitions or disks. VSS flags only the first partition, so it cannot import shadow copies for the remaining ones.

The remote machine sharing the volume runs a version of VSS that does not support remote shadow copy creation.

Confirm that the remote machine runs a supported version of Windows with all current updates applied. If the error persists, contact Druva Support.

A volume revert operation is already running. Only one revert can run at a time.

Wait for the current revert to finish, then retry the inSync backup. If the revert appears stuck, restart the VSS service and then restart the machine.

The active VSS provider does not support shadow copying the specified volume. This is typically a configuration or compatibility problem.

A duplicate VSS component with the same logical path and component name already exists, so VSS cannot proceed.

net stop vss

net start vss

2. If the issue persists, restart the machine to clear the stale VSS state.

3. Contact Druva Support if the error continues after the restart.

When inSync starts a backup, it creates a VSS snapshot of the backup folders. If snapshot creation fails with this error, the backup fails. The error indicates that a third-party VSS provider is registered on the system but its Component Object Model (COM) class is missing or broken.

A third-party shadow copy provider is registered in Windows but is not functioning. This commonly follows the uninstallation of software that registered a VSS provider without cleaning up the registration.

inSync Client log

[YYYY-MM-DD HH:MM:SS] [INFO] Windows VSS failed to create a snapshot for C:\ at step 5,

status 0x80040154 [Class not registered].

Windows event log (Source: VSS, Event ID: 12292)

Volume Shadow Copy Service error: Error creating shadow copy provider COM class on

CLSID {3e02620c-...} [0x80040154, class not registered].

Provider ID: {74600e39-...} Class ID: {3e02620c-...}

Step 1: Identify the third-party provider

vssadmin list providers

If more than one provider is listed, a third-party provider is present. Note the Provider ID shown in the event log.

Step 2: Force VSS to use the Microsoft provider

⚠️ Warning

Incorrect registry edits can prevent Windows from starting. Back up the registry and the machine before you make changes. In the Registry Editor, select File > Export to save a backup.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\BackupRestore

3. Right-click the key and select New > DWORD (32-bit) Value. Name it UseMicrosoftProvider.

4. Double-click UseMicrosoftProvider and set the value data to 1.

5. Click OK and close Registry Editor.

6. Restart the machine.

Step 3: Verify the fix

Why is my inSync backup failing with a VSS error?

Druva inSync uses VSS to create consistent snapshots during backup. VSS errors usually mean a required Windows service is not running, VSS DLL files are corrupted or unregistered, a third-party VSS provider is conflicting, or the volume has reached the 64 shadow copy limit. Start with the quick diagnostics.
​

How do I check which VSS writers are running?

Open an elevated Command Prompt and run

vssadmin list writers

All writers should show State: [1] Stable with no errors.

How do I re-register the VSS DLLs?

See Re-registering VSS DLLs for the full command sequence.

What is the maximum number of shadow copies per volume?

Windows supports a maximum of 64 shadow copies per volume. Once that limit is reached, no new shadow copies can be created. Delete the oldest with

vssadmin delete shadows /For=C: /Oldest

How do I force VSS to use the Microsoft provider instead of a third-party one?

See Error 0x80040154 for the registry steps that set UseMicrosoftProvider to 1.

My VSS error is not listed here. What should I do?

Contact Druva Support and provide the exact error code, the inSync Client logs, and the relevant Windows Event Viewer entries (Application and System logs, filtered by Source: VSS).

Where do I find the inSync Client logs?