How to Delete a Single Entry in TMB??

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Level 1

15 points

How to Delete a Single Entry in TMB??

Hello folks.

I have a 12TB TMB drive. I have ~8.5TB of data on other drives to back up. So, technically, I have room. This ~8.5TB includes the main boot-up drive, and three external HDDs.

The TMB drive, however, is full. While trying to perform a TMB op last night, I woke up this morning to the message that the drive was full, and could not complete the back-up operation.

The reason: I’ll try not to get into the weeds here, but... I replaced one of those external storage drives with a new one — but kept the same name for the new drive as the old (“Backup 2”). Backup 2 contains the contents of old Backup 2, plus a few weeks’s worth of additional files. I figured TMB would see this as a continuation of the normal back-up op for this disc, and just write the changes.

But, no. It thought it necessary to back the whole thing in full. Now, there is an old entry on the TMB disc that I no longer need. So...

Is there a way to delete a single entry / folder on a TMB drive? So far, I have not found a way. If not, will it be necessary to wipe the TMB drive clean and start over?!?

Thanks.

MacBook Pro 13″

Posted on Aug 20, 2026 10:22 AM

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Answer 1

Camelot

Level 9

60,969 points

Aug 21, 2026 1:18 PM in response to Keithiepoo

I think the overarching questions here have been answered, except for the one specific point...

> Is there a way to delete a single entry / folder on a TMB drive?

Yes... and no...

As previously noted, Time Machine wants at least 2x the amount of space that you're trying to backup. It obviously needs 1x the space for the initial copy, plus room for the incremental changes. In my option it's largely a rule of thumb, and everyone's case will differ based on rate of change (how much data you change on a daily/weekly/monthly basis), and how far back you want to maintain backups.

Someone that creates 100kB Pages documents and 200kB spreadsheets is going to have a much smaller increment that someone that's frequently editing 100GB video files, and someone that cares about going back a month is going to have different needs from someone that wants years of archives.

That said, and as already noted, Time Machine tracks backups by volume ID, not by name - when you replaced one of your source drives with a different disk, it got a new volume ID (the name is irrelevant), and Time Machine has no idea that it's contents are the same as the previous disk and will start a new backup cycle for this drive, and that is the crux of why you're getting the message - the previous 'Backup 2' backup is now essentially just an archive, and Time Machine will want to start a new cycle for the new 'Backup 2' volume.

There is a way to adopt an existing Time Machine backup to map to a new drive, but tbh I've never tried it on a multi-volume system, only when migrating from machine to machine, so I have no idea how it will behave when adopting only one of three volumes (maybe it'll work fine...?)

Either way, you can delete the backups, but it'll be tricky. On the Time Machine drive there are a number of folders based on time stamps. Inside each of these are more folders - one per backed up volume. To delete one volume's worth of backups you need to turn OFF Time Machine (so it doesn't try to backup while you're futzing with it's drive, then walk through ALL of the timestamp folders removing every occurrence of the Backup 2 folder. You'll need to get every one in order to recover the space.

Once done, re-enable Time Machine and you should be OK

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Answer 2

MrHoffman

Level 10

161,001 points

Aug 20, 2026 10:43 AM in response to Keithiepoo

I will guess “TMB” means Time Machine Backup, maybe?

Time Machine officially wants minimally twice the protected storage, and locally preferably closer to 2.5 to three times the size of the protected storage. Or more.

It would be usual to adopt the old Time Machine backup from the new Mac, if that is what happened here. If it adopted, then it’s using the backups, and it needs more storage for all that has changed.

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Answer 3

MrHoffman

Level 10

161,001 points

Aug 20, 2026 4:46 PM in response to Keithiepoo

TIme Machine isn’t going to pick up and continue with a full and subsequent incremental backups previously in progress from a now-gone archive on some now-gone storage.

TIme Machine keeps the backup status on the target storage volume, in the Time Machine archive, and not somewhere else within macOS.

Each Time Machine archive for a Mac has its own status too, allowing alternating between multiple targets.

If there is no Time Machine backup archive found on the target storage, or if the last backup found on the target is sufficiently archaic that making an incremental copy of “just” the changed files more work than it is worth, Time Machine will archive everything.

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Answer 4

Keithiepoo Author

Level 1

15 points

Aug 20, 2026 3:50 PM in response to Keithiepoo

Hello Mr Hoffman. Thanks for taking the time.

However, perhaps I wasn’t clear about something: I did not get a new computer, but a new storage drive. This was to replace another storage drive (of the same capacity, and its new replacement was given the same name, “Backup 2” — although, the older, failed Backup 2 was formatted as APFS case sensitive, and its replacement, merely as APFS... perhaps this caused Time Machine to “see” the drive as an entirely new volume).

It has also been my experience that, as long as the TMB (yes, “Time Machine Backup”) drive has more space than the data you need to throw on it, it has always backed up that data. Multiples of 2-4x were never required by the system.

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Answer 5

MrHoffman

Level 10

161,001 points

Aug 20, 2026 4:04 PM in response to Keithiepoo

If you erased the volume, it is a new volume, with no Time Machine contents.

If you tried to copy a Time Machine backup, that doesn't work at all well. Or at all.

The doubled or tripled space is to both allow large files to be backed up, and multiple copies.

Time Machine doesn’t work very well when run at its limits.

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Answer 6

Keithiepoo Author

Level 1

15 points

Aug 20, 2026 4:23 PM in response to Keithiepoo

TMB only write updates once the “base” files are copied over.

I also never said that I was making duplicate back-ups of the Time Machine drive itself. I simply wanted a replacement storage drive to be treated like its predecessor, and for the TMB system to continue where it left off, and just back up the updates to the contents of the new, replacement drive. But, like I said, for reasons I can only conjecture, TMB decided to treat the drive as a brand new drive, and tried to copy ALL of its contents WHOLE, not just the updates.

My question is, can one delete a single entry on a TM drive, or does one have to start from scratch and reformat that TM drive to get things going the way they were before?

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Answer 7

Keithiepoo Author

Level 1

15 points

Aug 20, 2026 6:23 PM in response to Keithiepoo

Let me add one more thing...

I just learned that, regarding the drive size, you are correct. But, in the years I’ve used the TMB system, I’ve never gotten a complaint from it, nor did I ever even notice this recommendation — until today, when I decided to reformat my TMB (time machine) drive and I got that message. Ugh.

It recommends at least 22TB. Not sure why. I don’t have anywhere near that much data, and the system wipes out older data to make room for new.

Oh well. When TMB tells me it can’t do the job for whatever reason, I’ll make the adjustments and put out a loan on my freakin’ house to buy a 22 Petabyte HDD. Sheesh.

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Answer 8

MrHoffman

Level 10

161,001 points

Aug 20, 2026 6:55 PM in response to Keithiepoo

I’m not aware of a 22 petabyte HDD.

Largest HDD I’m aware of is 36 TB, for those with a budget to match.

Network Attached and Direct Attached Storage with RAID-6 or RAID-10 (and approximately never RAID-5) can stitch together multiple smaller HDDs. I’ve been using 12 TB to 22 TB WD HGST Ultrastar DC HDDs for that, depending on price and availability. Lately, that’s been “high” and “no”.

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Answer 9

Keithiepoo Author

Level 1

15 points

Aug 20, 2026 7:01 PM in response to Keithiepoo

I was being facetious. I know there are no PB drives (yet).

"Network Attached and Direct Attached Storage with RAID-6 or RAID-10 (and approximately never RAID-5) can stitch together multiple smaller HDDs. I’ve been using 12 TB to 22 TB WD HGST Ultrastar DC HDDs for that, depending on price and availability. Lately, that’s been “high” and “no”."

Hmmm... something to toss around in the brain. Thanks.

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Answer 10

Keithiepoo Author

Level 1

15 points

Aug 21, 2026 2:07 PM in response to Camelot

That was indeed very helpful. Thank you. Unfortunately, I’ve since reformatted the TMB drive and have begun making a fresh run of backups.

There are two things during this process that have happened that I do not get...

The one drive currently being backed up is old, so it’s taking HOURS to complete. Okay. But, why is the TMB drive taking on >3.3TB when this drive only has 2.65TB on it?? Unless it backed up my boot drive before it started dealing with the mounted drives??

This, and one other drive also mounted (also in line for getting backed up), both dismounted on their own once during this process. I turned them off for a bit and then remounted them, and TMB seems to be picking up where it left off. But, I am mystified as to why this happened at all. I know USB is a bit flaky sometimes, and USB devices sometimes need to be disconnected and then reconnected. Both drives are getting 100% health ratings from DriveDx, assuming that’s a reliable application. Ugh.

Well anyway, thank you for the valuable input.

Keith

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