After a round of Windows Updates, I encountered the same error on two different servers at different clients. Both used BackupAssist that relied on Windows Server Backup. They both backed up to NAS’s but one NAS was connected as an iSCSI device and the other was mapped as a network share. The versions of BackupAssist were different, as well. One server was bare-metal, one was an ESXI VM. One was 2012 R1, one was 2012R2.
Among the things I tried were:
- Changing the time of the backup
- Resetting shadow copies
- Changing maximum size for shadow copies
- Changing the VSS mode
- Checking the status of VSS writers
- Restarting the servers
- Restarting backup devices
Eventually I found the backup code, 0x807800C5, on both servers. Googling yielded nothing but a number of other people with the same error running everything from Windows 7 to Windows 2012. After a lot of troubleshooting, I ended up renaming the backup destination that Windows Server Backup used, which gave the backup a clean slate of sorts. Both backups have succeeded since then.
The full error I received was:
(There was a failure in preparing the backup image of one of the volumes in the backup set.). Please review the event details for a solution, and then rerun the backup operation once the issue is resolved.