Time Machine Backups not completing

[pedzsan]

My Time Machine backup is not working and I am wondering what to do.

I have a M1 Max MacBook Pro with 64GB of ram and 4TB of disk. My backup target is an external USB attached 5TB HDD and it has backups dating fairly far back. The Time Machine Settings says that the target drive has 430 GB of space left. When I first connected the drive a day or two ago, it had over 1TB of space.

The backup starts and then starts going very slow. The progress bar right now for example is about half way across, it has copied 26GB, and has been running for an hour and it says that another hour remains.

When I open Terminal and cd into the drive, I see directories like 2026-03-12-033043.interrupted. There are currently 16 of these. I have interrupted once by hand. Other than that, the drive is directly connected and there has not been any power issues, etc. When I interrupted it, I did a health check via Disk Utility and I also booted in Recovery Mode and did a health check of the built in drive. The external drive had 26 snapshots and took hours to verify but completed without issues. The internal drive verified in less than a minute.

I don't keep the target drive connected all the time. About once a month, I connect it and wait for it to complete a backup or two and then disconnect it. This seems to have worked so far.

Are there any suggestions on what to do?

Update 2026-03-13 09:42 -- it seems to have worked this time. I don't think it matters but I flipped the option to allow backups from battery. One of the AI based comments is the interruption may be from power which, with a battery powered laptop doesn't make sense and I am 99% sure there hasn't been any power issues but I figured why not?

I got a copy of Time Machine Mechanic. Currently it is red but it doesn't really tell me anything I don't already know. The clean up is still progressing. There once was 16 "Interrupted" directories and now there are only 13. I assume as the cleanup progresses those will slowly disappear.

 

[!!!]

The Time Machine Settings says that the target drive has 430 GB of space left. When I first connected the drive a day or two ago, it had over 1TB of space.

The backup starts and then starts going very slow. The progress bar right now for example is about half way across, it has copied 26GB, and has been running for an hour and it says that another hour remains.

Sounds like a lot of data on your Mac's SSD has changed (or at least Time Machine thinks it has) and it's just taking a while to copy.

interrupted

I don't think it matters but I flipped the option to allow backups from battery. One of the AI based comments is the interruption may be from power which, with a battery powered laptop doesn't make sense and I am 99% sure there hasn't been any power issues but I figured why not?

Indeed, could very well be that as well.

There's another issue you can read about on these forums where TM will fail to backup certain files when your Mac is locked. Typically you'd see an error message about the file and it failing.

Time Machine Mechanic

I was going to recommend that, shame it doesn't offer anything helpful for you.

Be sure to let the cleanup happen, and check how long the next backup takes. If you haven't touched many files then it shouldn't take that long. If it still fails you may want to check if something in the background has gone awry on your Mac and is creating spurious data, or if your backup hard drive is failing (the slowness may be an indication).

 

[pedzsan]

Sounds like a lot of data on your Mac's SSD has changed (or at least Time Machine thinks it has) and it's just taking a while to copy.


Indeed, could very well be that as well.

There's another issue you can read about on these forums where TM will fail to backup certain files when your Mac is locked. Typically you'd see an error message about the file and it failing.

I was going to recommend that, shame it doesn't offer anything helpful for you.

Be sure to let the cleanup happen, and check how long the next backup takes. If you haven't touched many files then it shouldn't take that long. If it still fails you may want to check if something in the background has gone awry on your Mac and is creating spurious data, or if your backup hard drive is failing (the slowness may be an indication).

The next backup was quick. I have a Windows VM using Parallels that I start once a year to do my corporate taxes. That was the big hit I'm sure. Plus... I think there was an update in there as well.

 

[Fishrrman]

OP:

If you want backups that will complete every time, STOP using tm and start using either CarbonCopyCloner or SuperDuper.

That's my opinion and I'm not changing it...

 

[bogdanw]

Might be useful - TimeMachineStatus https://github.com/lukepistrol/TimeMachineStatus
"a simple status bar app that shows the status of Time Machine backups"

 

[benwiggy]

I have a Windows VM using Parallels that I start once a year to do my corporate taxes. That was the big hit I'm sure.

If you have a massive, multi-gigabyte file, then TM will copy the whole thing, every time it's modified. I'd recommend excluding that file (or the folder it's in) from TM, and making a copy of it some other way.

I've been using TM since Leopard, and generally, it's worked flawlessly, saving my life on many occasions. But it is "one size fits all" -- it has very little configurable options. It does what it does, and that's it.

 

[pedzsan]

OP:

If you want backups that will complete every time, STOP using tm and start using either CarbonCopyCloner or SuperDuper.

That's my opinion and I'm not changing it...

I use both 😀

 

[pedzsan]

If you have a massive, multi-gigabyte file, then TM will copy the whole thing, every time it's modified. I'd recommend excluding that file (or the folder it's in) from TM, and making a copy of it some other way.

I've been using TM since Leopard, and generally, it's worked flawlessly, saving my life on many occasions. But it is "one size fits all" -- it has very little configurable options. It does what it does, and that's it.

As I mention, I use it just once a year so keeping it on TM seems ok. I guess I could move it to my NAS. 🤔