Graciously shutdown external HDD enclosure?

"I would not turn off the power knowing the hard drive is busy. When to turn it off depends on if you have multiple file systems installed. Perhaps you don't want all file systems to be unmounted.

To be safe, you might consider performing an unmount first."

"about the Ubuntu thing, you can easily umount it

in case you don't know how to umount ...
assume that the External HDD has the dir /dev/sda1
press

Alt + F2

then type

konsole

then

umount /dev/sda1

or use the sudo command if it needs root permissions."