Two days ago, a breaker tripped while my PC was performing a backup. When power was restored, my NAS's LED blinked blue for quite a while. (I assume it was rebuilding the RAID-1 array or validating the drives.) Normal operation eventually resumed, with two solid blue LEDs.
Today, I'm finding my NAS unresponsive—the router doesn't list its DHCP entry, I can't access the NAS via its assigned IP, and holding the power button pressed has no effect. How can I safely restart it, if it won't respond to the power button?