Symptom

When a machine with a recovery partition is recovered through Full System Recovery (FSR), the partition is not recovered to its original state. Instead, a RAW (unformatted) partition is created where the recovery partition was. 

When Full System Backup (FSB) is then performed on the recovered machine, the backup logs show the following warning: "Skipping volume '\\?\Volume {xxxxxxxxx-xxxx-xxxx-xxxxxxx}\', it does not contain a recognized file system". This volume refers to the unformatted partition.

The warning is not shown when backing up any machine with a recovery partition. It only occurs when backups resume after such a machine has been recovered, i.e. after the recovery partition has been replaced with a RAW partition.

Solution

To prevent this warning, you have two options:

(a) Remove the partition. This is safe to do and will not affect backups.

(b) Format the partition as desired.