What is Time Machine doing for so long in Big Sur?

[camner]

In Catalina, with an HFS+ TM volume, when the TM menu bar icon stops showing that TM is running, the disk stops its activity.

Just upgraded to Big Sur, and started with a new TM drive (formatted APFS). Now I notice that after the TM menu bar icon shows that the hourly backup is complete (and the menu shows the same), the TM drive is chattering away (and the activity light is showing activity) for a long time.

The TM drive is a WD Red Plus 8T (WDBAVV0080HNC-WRSN) drive, which is 7200rpm and uses CMR.

What is TM doing here? I have only about 2TB of an 8TB TM drive in use, so TM isn't thinning.

 

[gilby101]

Spotlight probably. Is there activity from processes with names starting with md?

Or thinning. TM will thin the hourly backups down to daily ones.

 

[camner]

Yup! A lot of these processes! So, does Spotlight typically index Time Machine volumes? That's the drive that's thrashing away.


Is there really any point to indexing a Time Machine volume?

 

[Apple_Robert]

Yup! A lot of these processes! So, does Spotlight typically index Time Machine volumes? That's the drive that's thrashing away.
View attachment 1783778

Is there really any point to indexing a Time Machine volume?

Unless you want to be able to search said drive (although it may not be accurate) I would stop the indexing. I consider that a waste of time.

 

[ck1984]

It seems specific to the APFS Time Machine implementation.

My APFS Time Machine drive was indexing all the time; it seemed like it needed to re-index the whole drive after every backup. It might also have been triggered by detaching and re-attaching the drive. There were a bunch of forum posts around the Internet about the issue back when I encountered it, so it seems like a common issue. I'm guessing most people are still using old HFS Time Machine drives or just live it with, so it hasn't gotten lots of attention. (Or possibly there's a specific rare issue that triggers it.)

I think I tried removing it from Spotlight but IIRC there was an issue with that; either it wouldn't let me or it kept indexing it anyway. It was a while ago so might still be worth a try, but I'm guessing the indexing is part of the Time Machine process.

I went back to HFS and the problem disappeared. (I reformatted the drive for Time Machine on a different Mac with Catalina, which Big Sur then accepted. Not sure if there's a way to create it with Big Sur, but since the HFS implementation uses standard file system features, there's presumably a way to trick it into thinking it's an already-created Time Machine drive, maybe just format it as case-sensitive/journalled and create a Backups.backupdb folder?)

Hopefully Apple will clean it up in macOS 12.

 

[gilby101]

Yup! A lot of these processes! So, does Spotlight typically index Time Machine volumes? That's the drive that's thrashing away.

Yes, the Time Machine disk is indexed. It is an integral part of Time Machine to APFS (TMA). You can probably eject the drive and the md processes will gracefully exit to allow the disk to eject cleanly. It will then continue indexing next time you mount it.

Better to let it get on with indexing. I don't notice it for subsequent backups.

I went back to HFS and the problem disappeared.

But TMA is so much faster, reliable, robust, etc. than TMH.

Unless you want to be able to search said drive (although it may not be accurate) I would stop the indexing. I consider that a waste of time.

But I thought you didn't use Time Machine. Have you actually used TMA and stopped the indexing?

 

[lssmit02]

There are good reasons to use APFS instead of HFS+, one of which is the efficiency of the transfer, as explained in this article: Time Machine to APFS: How efficient are backups? The eclecticlight.com site has a lot of additional information about the transition to APFS with Time Machine. Of course, there are some drawbacks, but on balance I think the transition is worth it.