DPM2010–Exchange VSS backup error 0x800423F4

Sorting out DPM2010 backups of an Exchange 2003 server, and got an error:

The VSS application writer or the VSS provider is in a bad state. Either it was already in a bad state or it entered a bad state during the current operation. (ID 30111 Details: VssError:The writer experienced a non-transient error.  If the backup process is retried,
the error is likely to reoccur.
(0x800423F4))

I had a look at the VSS writer status on that server, and noticed this:

Writer name: ‘Microsoft Exchange Writer’
Writer Id: {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7}
Writer Instance Id: {dc79ccf4-f2a3-4031-9d1e-c59fc2f0a322}
State: [7] Failed
Last error: Non-retryable error

The Application event log had errors which didn’t explain much by themselves (Error code 0x80040102 when preparing for backup. ), but the data within the error log helped me sort out what the problem was:

Incr/Diff snaps not supported with Circular logging enabled.

I then remembered that we’d enabled circular logging on that server in the past because it was backed up using Symantec BESR.

I ended up restarting the Information Store, and then retrying the recovery point. All is well. There’s more information here about the various DPM Hyper-V related issues.