convergence

I recovered from the BTRFS corruption by formatting both cache drives, adding them to the pool, and restoring my data from a backup. Everything was successfully recovered except the corrupted file. Only one docker container was affected, and I'm fairly sure the file got corrupted by a dirty shutdown due to power loss.
 
I've kept the system running on unchanged hardware without any problems until early February 2023. Then -- one fateful morning -- I rebooted the machine and was notified of cache pool corruption shortly after. A scrub revealed that the same file had gotten corrupted as in 2022, albeit in an entirely different container that only had recoverable errors during the previous incident. Both containers (corrupted in '22 & '23) were running an Urbit image. The main difference was that I thought I had managed to do a clean reboot the second time.
 
The similarity between the incidents allowed me to figure out that the default shutdown timeout settings were insufficient for my setup. I have now increased the relevant timeouts and haven't had problems since. I'm still not entirely confident that every shutdown will be clean from now on, and I hope to find the time to investigate what takes so long in my shutdown sequence. I also don't understand how docker containers getting killed would cause BTRFS corruption... I understand that a file on the container's volume might get corrupted, but not how different data could be written to the disks of the pool (and without updating the checksums).