Microsoft Exchange Server Backup Error "VSS_E_FLUSH_WRITES_TIMEOUT"

31 Mar, 2025

Product Version

AhsayOBM: 7 and above

Operating System

Windows

Symptom

When performing a MS Exchange server backup, the following error message is received in the backup report:

[VSSDatabaseExpt] VSS_E_FLUSH_WRITES_TIMEOUT

Cause

The message is returned by the MS Exchange VSS writer.

It indicates the MS Exchange VSS writer was unable to successfully create a VSS snapshot of the MS Exchange database(s) within the default time period due to high disk activity on the server.

Resolution

Check if there is other I/O intensive application(s) that is running on the client computer at the time of the backup.
Try adjusting the backup schedule to another time when disk usage is low.
Check on the VSS writers:>/p>
- Open an Administrative command prompt and enter the following command:
```
vssadmin list writers
```
  This should output a list of writers and their status, they should all be reported as stable.
  If there is writer listed at unstable, re-register the Volume Shadow Copy Service by following the instructions below:
  - In an administrative command prompt, browse to ${OBM-Install-Home}\bin
  - Execute the 'RegisterVSS.bat' batch file.
  - Reboot the machine.
Ensure that left-over snapshots are cleaned up:
- Enter the following command in an elevated command prompt:
```
vssadmin delete shadows /all
```
  This will clean up all VSS snapshots.
  Defect operating system may often accumulate hundreds of VSS snapshots that persist in the system and cause Windows to become un-responsive.
In some cases, you may not be able to delete the VSS snapshots with the above command. Perform the following instead to resize the ShadowStorage:
- To decrease the maximum shadow storage size, enter the following command in an elevated command prompt:
```
vssadmin resize ShadowStorage /For=C: /On=C: /MaxSize=300MB
```
  If no VSS writer error is displayed, but the system is not creating a new VSS snapshot, increase the system's max shadow storage size instead.
- To increase the maximum shadow storage, enter the following command in an elevated command prompt:
```
vssadmin resize ShadowStorage /For=C: /On=C: /MaxSize=10GB
```