> you turn it off and on again That would be a power failure. Kernel crash is not equivalent to that. System reboot doesn't entail power failure either. The

> you turn it off and on again That would be a power failure. Kernel crash is not equivalent to that. System reboot doesn't entail power failure either. The disks may be powered by an independent external enclosure (e.g. JBOD). All they see is that they stopped receiving commands for a short while.