I tried to stop a qemu-img copy or clone and it broke everything. It was fine to "stop" it from the GUI but a process still persisted so I killed the relevant qemu-img and the kernel went crazy. It also may not have helped that I tried to lvremove a different volume (an unused disk). But either way it breaks LVM (you cannot even run lvdisplay) so a reboot is necessary.
Jan 17 06:45:21 testserver kernel: [ 5680.439337] systemd-udevd D 0&nbs........
hdparm -B 255 /dev/sdb
/dev/sdb:
setting Advanced Power Management level to disabled
HDIO_DRIVE_CMD failed: Input/output error
The one thing you can do though is to set hdparm spindown time lower (it doesn't seem to work that well).
-S set standby (spindown) timeout
hdparm -S 251 /dev/sda
/dev/sda:
setti........