When we back up Exchange, we create a snapshot with the help of the VSS of Exchange database.
The following actions can lead to the error causing loss of the snapshot:
- rebooting the server during the backup of exchange;
- restarting the DataShield Back and Recovery Service Controller during the backup of Exchange;
- restarting the Microsoft Information Store Service or the VSS during the backup of Exchange.
Most likely, this is a temporary issue and next backup will be successful.
NOTE: There is also a chance that the system deleted snapshot by itself. You should check event logs in the time frame +/- 10 minutes of the fail. In case VolSnap deletes the shapshot, you should tune your system to prevent it.