Hi All Hoping you can help me out after many years of running unraid i've run into a pretty big issue.
My Unraid server has had a a lot of dirty shutdowns recently that have been unavoidable (I'm buys a UPS Soon), however the last one has broken my cache drive.
The GUI is showing Unmountable: Unsupported or no file system next to the cache pool (2 NVME Drives (nvme0n1 & nvme1n1))
Ive had a look at the guidance link here
When I try to mount the disks I get the below
 

mount: /temp: wrong fs type, bad option, bad superblock on /dev/nvme0n1p1, missing codepage or helper program, or other error.
       dmesg(1) may have more information after failed mount system call.

When I try to do the restore I get the following

parent transid verify failed on 1529298944 wanted 1770240 found 1770241
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
Ignoring transid failure
WARNING: could not setup extent tree, skipping it
WARNING: could not setup csum tree, skipping it
WARNING: could not setup free space tree, skipping it
Couldn't setup device tree
Could not open root, trying backup super
warning, device 2 is missing
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
Ignoring transid failure
WARNING: could not setup extent tree, skipping it
WARNING: could not setup csum tree, skipping it
WARNING: could not setup free space tree, skipping it
Couldn't setup device tree
Could not open root, trying backup super
warning, device 2 is missing
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
parent transid verify failed on 1529298944 wanted 1770240 found 1770241
Ignoring transid failure
WARNING: could not setup extent tree, skipping it
WARNING: could not setup csum tree, skipping it
WARNING: could not setup free space tree, skipping it
Couldn't setup device tree
Could not open root, trying backup super

I have diagnostics before and after the array start and they're attached
 

unraid-after-array-start-diagnostics-20231207-2120.zip unraid-before-array-start-diagnostics-20231207-2119.zip

This error is fatal, and if btrfs restore doesn't work, I'm afraid not much else can be done with the existing btrfs tools, an app like UFS explorer may be able to recover some data, there's a free trail.