On Sat, Jan 30, 2021 at 1:59 AM Patrick Bihlmayer [off-list ref] wrote:

Hello together,

today i had an issue with my cache drive on my Unraid Server.
I used a 500GB SSD as cache drive.

Unfortunately i added another cache drive (wanted a separate drive for my VMs and accidentally added into the cache device pool)
After starting the array and all the setup for the cache device pool was done i stopped the array again.
I removed the second drive from my cache device pool again.

I started the array again - formatted the removed drive mounted it with unassigned devices.#
And then i realized the following error in my Unraid Cache Devices



Unfortunately i cannot mount it again.
Can you please help me?

I don't know anything about unraid. The attached dmesg contains:
[ 3660.395013] BTRFS info (device sdb1): allowing degraded mounts
[ 3660.395014] BTRFS info (device sdb1): disk space caching is enabled
[ 3660.395014] BTRFS info (device sdb1): has skinny extents
[ 3660.395733] BTRFS error (device sdb1): failed to read chunk root
[ 3660.404212] BTRFS error (device sdb1): open_ctree failed

Is that sdb1 device part of the unraid? Is there a device missing? The
'allowing degraded mounts' message along with 'open_ctree failed'
suggests that there's still too many devices missing. I suggest a
relatively recent btrfs-progs, 5.7 or higher, and provide the output
from:

btrfs insp dump-s /dev/sdb1


-- 
Chris Murphy