> Well, what can we try instead?
> write to the mounted disk anyways. fuck you

Stupid penguin trick I learned: Add a file inside ramdisk (i use /dev/shm) as LVM PV.

pvmove off the hard drive

Boom, now your OS lives entirely in RAM

You can now even replace the hard disk, put a new one and migrate back.

Or migrate to network storage (nbd,iSCSI etc.), re-sequence disks into whatever RAID you need, and migrate back

Need to fix /boot after that tho, and probably make sure to not have power failure in meantime