Time Machine disk stays active long after backup and "cleaning up" is finished.

Is this a form a clean-up because the drive is so full?

In a manner of speaking, yes. It's very normal for Spotlight indexing to take a long time after changes are made to the backup drive. That amount of time will be greater not strictly because the TM backup drive is "full" (which will always be so) but is probably due to the great number of files it contains. That number is likely to be in the tens of millions, given the capacity of your TM backup drive (10 TB).

I suspect what you are describing is normal. Let Spotlight work.

... is there anything I can or should do to free up space on the drive?

No. Never do that, unless you want to completely erase the backup drive. That's ok.

Advanced learning tip: though you did not explicitly ask, there is never a need to worry about drive failure — unless — that is your one and only backup drive. If backups are important to you always have two (preferably more) separate and redundant backup devices. And if one of those two fail, guess what. You're down to only one.

snsok wrote:

Sonoma 14.1.1, MPB M1 64GB/2TB, WD Elements 10TB HDD 5 yrs old

After a Time Machine backup, this HDD stays active. I can feel the activity through the surface of my desk. The drive has been full except for around 100GB.

Time Machine does usually spend some time in "cleaning up" which I expect with a mostly full hard drive, but the activity continues long after Time Machine on the menu bar just indicates the time of the last backup.

Activity Monitor only shows "WindowServer" and "mds" as processes with any significant "%CPU" consumption.

I saw another thread here mentioning possible drive failure. Other than this prolonged activity, it seems to be working OK and I am able to retrieve a few files just as a test/

I had to take the laptop out of hte house yesterday. When I reconnected it to the Time Machine drive, it accomplished its daily backup...and then 45 min later, it's still doing something even without "cleaning up" showing on the Time Machine menu drop down.

The strange activity finally ends around 1 hr after the last backup.

The activity is not continuous. It does start and stop. This doesn't sound like a drive failure.

Is this a form a clean-up because the drive is so full? If so, is there anything I can or should do to free up space on the drive?

The only Safe way to remove files from the drive is from within Time Machines Backup Utility

Any Other methods posts ALL you backups at High Risk of be Corrupted

That I believe, is Not What you want

User wrote " Sonoma 14.1.1, "

That shipped some time ago

Current version is presently @ 14.4.1

Keep your Mac up to date

About the security content of macOS Sonoma 14.4.1

Always make a Time Machine Backup  before doing any upDates

To truly protect your non replaceable Data - have a 3-2-1 Rescue Plan in place and always current

3 Backups using 2 methods and 1 off site incase of natural disaster or un-natural disaster.

Each of the above should be done to a Dedicated Single Purposed External Drive 

I must openly offer my apologies for Bad and Incorrect inform on pruning TM Backup Drives

No excuses on my part

Moving forwards

If as you mention this " WD Elements 10TB HDD 5 yrs old " is a Dedicated drive used only for TM Backups

The options seem clear

Get another External Drive with a Greater Drive Capacity and set it up for Backups

Set aside the existing " WD Elements 10TB HDD 5 yrs old " for safe keeping

Then, Wipe that Drive and use that same drive for TM Backups

https://apple.stackexchange.com/questions/427300/how-can-i-manually-delete-files-and-folders-from-a-time-machine-backup-volume

snsok wrote:

All: so can I correctly assume the lengthy disc activity is related to housekeeping? The drive, being essentially full, needs to purge some space after each backup session?

It would be reasonable conclusion

I should add that it’s configured as encrypted, which I’ll assume adds

more overhead.

That too seems reasonable.

This ext TM drive is backing up the internal 2TB drive, one 4TB SSD and one 5 TB HDD. Total storage on those active drives is about 7.5 TB

Sorry about this, maybe a faux pas but backing up to any Internal Drive(s) is not really recommended

Given that, won’t any size drive eventually have the same issue over time as it fills up with archived files?

The Theory, TM Backup Utility should make space as required to accommodate new Snap Shots

But, it does not always do that

Another reason indexing a TM drive takes so long is because of all the hard links used to keep the size of the backups down.

snsok wrote:

Thanks. Typo on Sonoma. Actually on 14.4.1

> The only Safe way to remove files from the drive is from within Time Machines Backup Utility

Is this separate from the Time Machine app? I don't have any time machine utility other than the actual Time Machine app that lives on the menu bar. When I go into Browse Time Machine Backups, there is no option to delete any files that appear in the stacked time machine finder windows.

I recall from a post year a while back that removing individual files from teh backup drive wasn't possible.

Since one appear took about Not Deleting files from TM Backup drive

Why would one ask to "If so, is there anything I can or should do to free up space on the drive? "

> The only Safe way to remove files from the drive is from within Time Machines Backup Utility

Something new? Where in the Time Machine application do you see the option to delete or remove files?

Please provide step-by-step instructions.

PRP_53 wrote:

https://apple.stackexchange.com/questions/427300/how-can-i-manually-delete-files-and-folders-from-a-time-machine-backup-volume

That article os over 2 ½ years old. That feature went out at least 3 systems ago (counting back from Sonoma). We can no longer Control (right) - click on a time in Time Machine and remove all instances of a file/folder from Time Machine. ☹️

The OP told us up front that he was running Sonoma. You must have missed that, even though it was the first item mentioned in the post.

Your reply linked to an article that has not been relevant in about 3 years, maybe more.

Old Toad wrote:

PRP_53 wrote:

https://apple.stackexchange.com/questions/427300/how-can-i-manually-delete-files-and-folders-from-a-time-machine-backup-volume

That article os over 2 ½ years old. That feature went out at least 3 systems ago (counting back from Sonoma). We can no longer Control (right) - click on a time in Time Machine and remove all instances of a file/folder from Time Machine. ☹️

https://discussions.apple.com/content/attachment/630d7577-3c23-47c5-a885-7b52fc5b8761

Thank you @Old Toad 😎

I needed my wings clipped a bit 😔

Bob Timmons wrote:

The OP told us up front that he was running Sonoma. You must have missed that, even though it was the first item mentioned in the post.

Your reply linked to an article that has not been relevant in about 3 years, maybe more.

Thank you @Bob Timmons 😎

I needed my wings clipped a bit 😔

Sometimes, at this age there are Brain f**ts