But is the RAID handling remotely sane yet? See https://arstechnica.com/gadgets/2021/09/examining-btrfs-linu... It has gems such as: * It won't boot on a degraded array by default, requiring manual action to mount it * It won't complain if one of the disks is stale * It won't resilver automatically if a disk is re-added to the array I think the first is the killer. RAID is a High Availability measure. Your system is…
Many folks I know who manage storage don't make the boot volume RAID (redundant)- instead, it's some rapidly duplicatable thing like an NMVE flash containing the root filesystem, and there's a replacement handy. Then you can bring up and bring the full power of userspace to bear on the RAID repair.
RAID is used for two things:
1. improving the performance of slow disks (at least the read performance) 2. having 1/2 disk fail with your system remaining completely usable, till you replace the faulty disk as soon as possible.
The second point is fundamental to me: there shouldn't be any disruption of service whatsoever, meaning that only the sysadmin should notice the fault (beside maybe a reduced performance of the system since you have 1 less drive). Database transaction that were in progress when the disk did break shouldn't fail, writes/reads on the FS shouldn't fail, the only thing that should happen is an alarm triggered in the monitoring system to inform that a disk needs to be changed as soon as possible.
Having a RAID with manual recovery... it means that you could end up a Saturday evening in front of a computer to bring a system back online, and still some data corruption may have happened.