September 6, 20223 yr Hi I had two drives pooled to create a BTRFS (RAID1) cache, but overnight one of them has failed and gone offline. The second drive is still present and has a green ball, but shows an unmountable file system unRIAD wants me to format it. How can I recover from this situation? I assumed that in the case of a drive failure the pool would just keep running and alert me to replace the failed disk.
September 6, 20223 yr Author Hi @JorgeB please see attached. I've not touched the failed drives but I have restored a backup of a VM onto the main array as it's critical for my work. unga-diagnostics-20220906-1331.zip
September 6, 20223 yr Community Expert Looks like there's superblock damage to that device, do you still have the other one?
September 6, 20223 yr Author The SSD that went offline? Yes it's physically still installed in the server, I've not disconnected anything. It seems odd that one would physically fail and the other would sustain virtual damage in the same event.
September 6, 20223 yr Community Expert Try power cycling the server (not just rebooting) to see if the other device comes back online, if it doesn't there are some recovery options here.
September 7, 20223 yr Author 18 hours ago, JorgeB said: Try power cycling the server (not just rebooting) to see if the other device comes back online, if it doesn't there are some recovery options here. A physical power cycle has made the drive visible again on the system but it's now an unassigned device, and not in the 2 disk cache pool. When I add it back to pool, unRAID tells me that the drive will be formatted when I start the array. Is there a way to add it back in correctly?
September 7, 20223 yr Community Expert Unassign all cache devices, start array to make Unraid "forget" current cache config, stop array, reassign all cache devices (there can't be an "All existing data on this device will be OVERWRITTEN when array is Started" warning for any cache device), start array and post new diags.
September 7, 20223 yr Author Unfortunately the failed drive (cache drive 1) seems to have a physically failed and has disappeared from the system again. The remaining drive has the 'bad superblock' error and none of the safe (or unsafe) recovery methods mentioned in your (excellent) btrfs thread work. It won't mount at all. I have backups, they are just a few days out of date. I'll create a new 1 drive cache pool and restore to the working drive. I'm disappointed that BTRFS dropped the ball here, a RAID1 configuration should be able to sustain a 1 disk failure without catastrophic results. 🤷♂️
December 19, 20223 yr On 9/7/2022 at 5:19 AM, JorgeB said: Unassign all cache devices, start array to make Unraid "forget" current cache config, stop array, reassign all cache devices (there can't be an "All existing data on this device will be OVERWRITTEN when array is Started" warning for any cache device), start array and post new diags. Does this mean losing all the data from the pool? Or does this actually recover the previous state?
December 19, 20223 yr Community Expert 1 hour ago, Goguleanu said: Does this mean losing all the data from the pool? Or does this actually recover the previous state? It won't delete anything, as long as you don't format the pool after start if it doesn't mount, as for recovering depends on the situation.
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