So one of my drives was acting up, so I stopped the array and then pulled out one of the drives for my other pools by accident. It appears doing so, caused it to get an error message.

When running btrfs fi show I get the following

Label: none  uuid: 20662da0-afcb-4ae1-bc89-cd6d2cf8e959
        Total devices 4 FS bytes used 20.00TiB
        devid    2 size 2.73TiB used 2.73TiB path /dev/sdx1
        devid    3 size 2.73TiB used 2.73TiB path /dev/sdah1
        devid    4 size 12.73TiB used 12.68TiB path /dev/sdg1
        *** Some devices missing

I've tried to reboot the server and the issue is still there. Any ideas on how I can recover it without losing any data?

unraid-diagnostics-20260101-1913.zip

What profile was the pool using? According to the syslog, it wasn't redundant, at least not fully:

Jan 1 17:38:49 UNRAID kernel: BTRFS warning (device sdx1): chunk 19980285378560 missing 1 devices, max tolerance is 0 for writable mount

Jan 1 17:38:49 UNRAID kernel: BTRFS warning (device sdx1): writable mount is not allowed due to too many missing devices

I believe it was set as RAID 0. I didn't really care about the data. Is it possible to recover it without losing everything?

RAID0 requires all the devices present; the only option to try and recover the data is if the old device still exists.

If it's failing, you can try cloning it to a new one with ddrescue, then use that one with the pool. Depending on how successful the clone is, it may allow you to recover most of the data.

I'm a bit confused. That pool only has 4 drives and are they not all present? UNRAID shows green on them. I'm also not seeing any failed SMART reports for any of the drives.

5 hours ago, obesepanda said:

That pool only has 4 drives and are they not all present?

On 1/2/2026 at 12:23 AM, obesepanda said:

Total devices 4 FS bytes used 20.00TiB
        devid    2 size 2.73TiB used 2.73TiB path /dev/sdx1
        devid    3 size 2.73TiB used 2.73TiB path /dev/sdah1
        devid    4 size 12.73TiB used 12.68TiB path /dev/sdg1
        *** Some devices missing

Nope, one is missing the btrfs signature at least. Post the output from fdisk -l /dev/sdag

root@UNRAID:~# fdisk -l /dev/sdag
Disk /dev/sdag: 2.73 TiB, 3000592982016 bytes, 5860533168 sectors
Disk model: TOSHIBA HDWD130 
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 16773120 bytes
Disklabel type: gpt
Disk identifier: 31A4A078-D172-40EE-B09B-649E600FEB4E
Device     Start        End    Sectors  Size Type
/dev/sdag1    64 5860533134 5860533071  2.7T Linux filesystem

I get the following when running it.

The partition is there, sugegstin ghr disk was removed from the pool, post output from

wipefs /dev/sdag1

Despite the name, that won't wipe anything as written, and also

dd if=/dev/sdag bs=16M status=progress 2>/dev/null | hexdump -C | grep '_BHRfS_M'

Let it run for a couple of minutes and post the output, if trhere's any.

I let it run for about five mins and got the following

root@UNRAID:~# wipefs /dev/sdag1

DEVICE OFFSET  TYPE  UUID                                 LABEL
sdag1  0x0     xfs   d0b9fbf1-53f0-4560-9002-3cef4869bdde 
sdag1  0x10040 btrfs 20662da0-afcb-4ae1-bc89-cd6d2cf8e959 
root@UNRAID:~# dd if=/dev/sdag bs=16M status=progress 2>/dev/null | hexdump -C | grep '_BHRfS_M'
00018040  5f 42 48 52 66 53 5f 4d  9f 3f 01 00 00 00 00 00  |_BHRfS_M.?......|
04008040  5f 42 48 52 66 53 5f 4d  9f 3f 01 00 00 00 00 00  |_BHRfS_M.?......|

That looks like where I would expect the superblock and backup superblock to exist on a standard Unraid partition layout. What do you get from:

btrfs-select-super -s 1 /dev/sdag1

root@UNRAID:~# btrfs-select-super -s 1 /dev/sdag1
using SB copy 1, bytenr 67108864

And now again btrfs fi show

It looks like it's still showing the same thing

Label: none  uuid: d5aaad24-9cef-4355-873e-2785ad43db0d
        Total devices 4 FS bytes used 3.84TiB
        devid    1 size 1.82TiB used 1.82TiB path /dev/sde1
        devid    2 size 1.82TiB used 1.82TiB path /dev/sdc1
        devid    3 size 232.88GiB used 232.88GiB path /dev/nvme1n1p1
        devid    4 size 232.88GiB used 232.88GiB path /dev/nvme2n1p1

Label: none  uuid: d452fc5f-ee99-46fa-9bbe-682ab68e56c2
        Total devices 2 FS bytes used 120.68GiB
        devid    1 size 447.13GiB used 146.01GiB path /dev/sdd1
        devid    2 size 447.13GiB used 146.01GiB path /dev/sdf1

Label: none  uuid: f55cb54a-2452-494e-9340-9780bde56654
        Total devices 1 FS bytes used 10.10GiB
        devid    1 size 447.13GiB used 15.02GiB path /dev/sdj1

Label: none  uuid: 851912fa-e718-4fdd-8c29-7d58c7cfb7bf
        Total devices 2 FS bytes used 332.00KiB
        devid    1 size 223.57GiB used 2.03GiB path /dev/sdl1
        devid    2 size 223.57GiB used 2.03GiB path /dev/sdk1

Label: none  uuid: f67d589a-9d63-4c57-866d-b0508a799559
        Total devices 1 FS bytes used 163.14GiB
        devid    1 size 232.88GiB used 231.02GiB path /dev/nvme0n1p1

Label: none  uuid: 89cf4528-ee9b-4964-8291-4bc0331a689b
        Total devices 1 FS bytes used 17.75GiB
        devid    1 size 60.00GiB used 35.02GiB path /dev/loop2

Label: none  uuid: 63882d78-2006-4da2-85af-93eb4cbb5910
        Total devices 1 FS bytes used 2.76MiB
        devid    1 size 1.00GiB used 238.38MiB path /dev/loop3
warning, device 1 is missing

Label: none  uuid: 20662da0-afcb-4ae1-bc89-cd6d2cf8e959
        Total devices 4 FS bytes used 20.00TiB
        devid    2 size 2.73TiB used 2.73TiB path /dev/sdx1
        devid    3 size 2.73TiB used 2.73TiB path /dev/sdah1
        devid    4 size 12.73TiB used 12.67TiB path /dev/sdg1
        *** Some devices missing

Strange, there should be some btrfs filesystem on that disk. Maybe it's in conflict with another one. What does this output?

mkdir /x

mount -v /dev/sdag1 /x

I ran the first line once then ran both the commands at once, it's prolly why it says '/x' exists.  

root@UNRAID:~# mkdir /x

mount -v /dev/sdag1 /x
mkdir: cannot create directory ‘/x’: File exists
mount: /x: can't read superblock on /dev/sdag1.
       dmesg(1) may have more information after failed mount system call.

I'm afraid something is wrong with that superblock (and its backup), since the pool is not redundant and there's a missing device, not much else can be done AFAIK, maybe a file recovery app like UFS Explorer could recover something; the free trial should show if it can.