AS5104T Raid1 gets set to read-only and the fix

[Thorstor]

This has happened to me twice.

From the web interface there is no sign of any issue. The drives are good, everthing looks happy. But if you type "mount" at he SSH command line you see all mounts on the raid volume are read-only.

The first time I spent hours at the command line, got nowhere, reset and with much irritation started all over.
The second time was heading the same way. I've learnt a lot about BTRFS, but couldn't figure out how to unmount everything, thinking I needed to do a btrfs check --repair. The ".@plugin" mount point didn't seem to have a reason/running process to be busy but was.


Set-up - AS5104T, 2x Seagate Ironwolf 8 TB drives, formatted btrfs, mounted as single raid1 volume. Using SMB service so Windows PCs can back up to it.

Probable cause - I think the volume gets set read-only when it runs out of space. After the first time I reduced the max number of snapshots kept, thought there was lots of room, but a year later it shows nearly full. I've now removed all snapshots. Going read-only when full like this is really a bug and should be fixed. Doing a test run before snapshot removal it went read-only part way through a Windows PC backup program writing files to it.

The fix, fortuitously found and very simple, can be done from the web interface.
- first stop all file services, you don't want anything writing to the storage and kicking it back to read-only immediately.
- go to web interface Storage Manager > Drive. Select the first drive and the Disk Doctor button/OK. Repeat for the remaining drives.
- wait! The Disk Doctor scan takes a long long time and must complete on all drives. I think it may just be doing a btrfs scrub on the drives???
- from the user-name menu select restart/confirm and you are done. For me at least it boots back up read-write.
- delete files, snapshots until you have lots of free space. Note if you delete snapshots it takes time to complete, the free space will be seen to slowly increase.
- I suggest another reboot at this point to allow the OS to tidy up.
- re-enable the services you use and you should be good.....