I have an external 1TB USB drive (mechanical, not flash) dedicated as a Time Machine backup. It is completely handled by MacOS/Time Machine.
Is it safe to unplug it at any time, including while a backup is running? I am aware how this stuff works generally (missing cached data, corrupting internal file systems data structures, journaling etc.), but would like to know if Time Machine is – together with journaling – robust in this regard for devices dedicated to it.
It would be acceptable to lose the currently running backup; I just want to avoid corrupting the filesystem or the Time Machine state on it so much that I have to reformat.
EDIT: Someone mentioned the "Golden Rule" of always ejecting. This question specifically asks whether this Golden Rule is relevant to Time Machine-managed devices, or whether Apple has gone out of its way to make a Time-machine-managed device immune to the usual problems of unplugging during use.
Best Answer
Golden Rule - eject a drive before disconnecting it.
Even if it doesn't appear to be busy.
999 times out of a thousand, you'd get away with it - it's just that one last time that will completely wreck your file system.