Volume failed to mount and the message "kernel: XFS: failed to locate log tail" is recorded in the log.
Following a power outage or crash, the system may fail to mount a volume with the follow messages displayed in the log.
kernel: XFS: failed to locate log tail
kernel: XFS: log mount/recovery failed
kernel: XFS: log mount failed
These messages are an indication of file system corruption. Typically file system corruption will occur when metadata changes to the file system are not able to be written. This is most common after a system power outage or crash event. In this specific case, the file system itself is damaged and is unable to be accessed.
Guardian OS has a built-in tool to address this issue that may be able to repair the file system. In some cases it is not able to repair the file system and data will need to be restored from backups.
Steps to run a file system repair:
Log into your SnapServer web interface.
Navigate to Maintenance -> Tools
Select the volume or storage pool you wish to repair from the drop down menu.
Select 'Repair errors (aggressive)'
The aggressive repair is required for log tail, log mount and log mount failed errors.
Note: This repair can take a very long time as it is dependent on the size of the volume or storage pool, how much data is contained on that volume or pool and lastly how much damage is present. It is not unexpected to take several hours, or in some cases days if the damage is severe and the data set is very large (in excess of 16 TB).
On older SnapServers running a 32-bit file system (Versions 6.x and older) it may not be possible to scan file systems larger than 16 TB as they cannot address enough memory to map the file system. File systems larger than 16 TB may require 8GB or more RAM to scan and repair.
Keep in mind the Snap servers support automatic shutdown via an APC UPS as well as several popular backup applications. As always, it is best to be prepared with a backup plan for emergencies.