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Title
Backups fail due to VSS timeouts related to System Writer -
Description
You are attempting to backup a Windows 2012R2/2012 system using Rapid Recovery 6.x or AppAssure 5.x.
The backup fails after 10 minutes with an error message related to VSS timeouts. The Windows System log shows that there may be an issue with the System Writer. Specifically you find the following error message:
"Volume Shadow Copy Service error: Unexpected error calling routine RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,…). hr = 0x80070005, Access is denied."
After the attempted backup the VSS subsystem is in an unstable state and needs to be reset.
After reset, when you run
VSSAdmin list writers
The System Writer is shown as expected, in a stable state.
However, when you try to find it in the registry, as a subkey of
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Diag,
you are unable to find it.
There are several possible Event IDs associated with this error. The most common are 8193 or 126728.
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Cause
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Resolution
The most common case for this issue is the installation of the DHCP Server role.
This re-writes all the permissions on the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Diag
registry key but omits to add the "Network Service" back on the ACL list.
As a result, the Cryptographic service which governs the System Writer is unable to access the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Diag
registry key.
Specifically, the Cryptographic Service, which runs under the "Network Service" account, initializes the System Writer at every restart.
To fix the issue all that needs to be done is to add the "Network Service" Account with full permissions to the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Diag
registry key and restart the Cryptographic service. Once this is done, the System Writer key shows up in the registry and the backups are successful.
For a detailed description of the issue, please check the following Microsoft article: microsoft KB article