If there is un-written cached data there is a capacitor bank that allows this data to be quickly written to non-volatile flash and rw heads to be retracted in t

If there is un-written cached data there is a capacitor bank that allows this data to be quickly written to non-volatile flash and rw heads to be retracted in the event of power loss. They test this feature pretty heavily, esp. in enterprise drives. Source: used to work for an HDD manufacturer. So, they might be lying to you but it is pretty useless information on for modern drives.