external drive shows disk activity for several minutes after time machine completes backup; what's going on?

Question

Level 1

121 points

external drive shows disk activity for several minutes after time machine completes backup; what's going on?

I'm curious. Why does the external drive continue to show disk activity after a time machine backup is complete? I sometimes wait for it to quit before ejecting; other times I eject after the backup is done. Doesn't seem to make a difference in the backup data. I don't recall this happening with my old MacBook Pro.

Mac Air M1; OS 11.4; HITACHI 1TB HDD

thanks for any information...

MacBook Air 13″, macOS 11.4

Posted on Jul 27, 2021 12:44 PM

Answer 1

Jul 28, 2021 9:52 AM in response to Peter dErrico

After Time Machine finishes backing up, Spotlight catalogs the drives since it senses a change.

You cannot disable Spotlight from cataloging the Time Machine drives because Time Machine requires Spotlight when recovering files.

Answer 2

steve626

Level 7

20,243 points

Jul 27, 2021 8:05 PM in response to Peter dErrico

I am on Catalina but see this all the time and it lasts longer with rotational drives being used for Time Machine versus SSDs (I use both). My belief is that this is the computer indexing the backup drive since some new or changed files have been placed on it. This is to enable you to search through Time Machine backups. And such activity would be faster on an SSD than rotational drives. If you can, check activity monitor and if you are fast enough you may see some processes named something-"mds" which are indexing activities.

Answer 3

Peter dErrico Author

Level 1

121 points

Jul 28, 2021 11:21 AM in response to woodmeister50

Aha. That makes sense. When I first noticed it I thought that might be what's going on, but I dismissed the thought because I didn't realize Time Machine uses Spotlight. I didn't bother to look at spotlight preferences and see that the drive can't be excluded.

Thanks.