I have 2 vms which reside on the cache pool (2 nvme drives) today they both stopped working and I cannot restart them, I receive an error that the file system is read-only. On the main tab the cache shows plenty of space left, but the number of writes is 0 (reads looks normal) 

 Diags are attached. Any help is greatly appreciated!

floserver-diagnostics-20210406-1530.zip

I rebooted the server, and now neither cache drive is showing, I've had this problem before, see this thread. I went a while without issue, but seems to be back to the same problem again where the cache drives don't show up.

After rebooting the server 4 times, they are again showing up, but as unassigned devices.

Apr  4 04:40:03 floserver kernel: BTRFS error (device nvme0n1p1): error writing primary super block to device 2

Syslog doesn't cover the beginning of the problem but this suggests NVMe devices are dropping offline, see here fore better pool monitoring.

 

Also post new diags after the reboot.