I am using three external hard drives with Time Machine in rotation. Time Machine and I are confused as to which HD to use next.
TM will back up to whichever drive is connected. If more than one is connected, it will alternate/rotate through them with each hourly (if that’s set) backup.
Personally, I also keep three backups for 5 Mac’s in the house. One set is on a local 10 TB NAS (each Mac has a dedicated volume), the other two sets are on a pair of 4 TB SSDs (each Mac has a dedicated partition/container) to which I back up once a week and swap the drive to an offsite location.
I also have partitions that I would like to remove.
For that, you’d need to reformat the external drive.
Is there a way to copy the contents of all three external disks to my Mac (I have lots of space), reformat the external hard drives, and copy the files back onto them?
No. If you reformat the drive, you’ll have to select it as a ‘new’ destination in TM and start the backups from scratch.
I’ve had to do that occasionally, when a backup gets unstable.
(Side note – you could probably copy the .sparseimage bundles into your internal drive then back after reformatting, and TM might ask to assume the backups. But that will likely lead to corruption problems down the line, a fresh start is best.)
I would shut off backing up to iCloud while this is going on to avoid confusion and massive uploads there.
TM doesn’t back up to iCloud. File syncing with iCloud will not affect the TM process, there’s no need to turn it off.
