User profile for user: poiuytrewsdfghjk
poiuytrewsdfghjk Author
User level: Level 1
30 points

Time Machine - "Time Machine was only able to complete xxx% of the backup because there is insufficient free space on the backup disk."

I've been having this problem for a few years, and through a few Mac.


At some point Time Machine stopped overwriting old backups to make room for new ones, as it's supposed to. Time Machine used to be very much a set it and forget it backup, but now it just adds new backups until the external hard drive is full.


I have a 1TB M4 Mac Mini with a 4TB backup hard drive, but this problem started with my M1 Mini and a 2TB external. I do not know which OS update it was, but a few years ago Time Machine just stopped overwriting.


I contacted Apple, but they have been completely unhelpful, repeatedly suggesting I just get a larger external, or load up on iCloud. When I bring up that Time Machine had an overwrite functionality which no longer works the Apple-ites just tell me that it does overwrite. It's like they are gaslighting me. I spent an hour on chat - again - with them last night, all the best they could say was they would file my complaint.


I have restarted, re-installed, first aided, wiped and erased, and as I said I even got a new computer and multiple hard drives. At this point I'm assuming this is not a bug but a feature to push people to getting larger and larger iCloud service accounts, which feels like something Intel or Microsoft would have done back in the day.


But if anyone has a suggestion that does not include all things I've tried, if there is some setting I'm missing, please let me know. Otherwise I'm stuck wiping and reloading a hard drive every few months if I want an on-site backup.

iMac (M4)

Posted on Mar 2, 2025 10:49 AM

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User profile for user: poiuytrewsdfghjk
poiuytrewsdfghjk Author
User level: Level 1
30 points

Mar 2, 2025 11:12 AM in response to xWauwau

Yes, I've thought about and done that, but it kinda is like having a car that says it gets three dozen miles per gallon of gas... but only if you let it roll down a hill the last dozen.


If I have to do that extra work for Time Machine it has lost a basic functionality, which Apple insists it has. Sure I can do the deletions, but I remember when Apple's slogan was it just works.

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User profile for user: Charles Palenz
Charles Palenz
User level: Level 2
394 points

Mar 3, 2025 7:06 AM in response to poiuytrewsdfghjk

Three years ago I bought a MacStudioM1 with 4TB internal (1.2TB used) and a new external 6TB HD dedicated for Time Machine and the backups go to June of 2022, and it tells me I have 3.98TB available. The author, poiuytrewsdfghjk would seem to be in a similar hardware situation with a large Time Machine backup drive compared to a smaller internal HD. Sequoia is now my third OS and never an issue, so there must be a dynamic we are not aware related to the hardware. Make sure the HD is APFS (Case-sensitive) and freshly formatted, dedicated, connected directly to the mini (no hub) and start time machine. In my case I have not reached the overwrite stage, but neither should you. And if you have already done what is suggested, the HD would be possible suspect.

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User profile for user: xWauwau
xWauwau
User level: Level 2
164 points

Mar 2, 2025 10:55 AM in response to poiuytrewsdfghjk

I know this may not be any helpful, but wouldn’t you just be able to delete old backups manually? Have you thought about that? And according to Apple, as you said, Time Machine should overwrite old back ups automatically, so that should not be necessary at all, but at least it should be a workaround.

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User profile for user: xWauwau
xWauwau
User level: Level 2
164 points

Mar 3, 2025 4:26 AM in response to poiuytrewsdfghjk

You’ve certainly got a point there, and I believe most of us understand your issue, but unfortunately, as long as Apple is not willing to fix the problem, you’ll probably not have any choice except from switching to another system, which I wouldn’t personally do.

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User profile for user: poiuytrewsdfghjk
poiuytrewsdfghjk Author
User level: Level 1
30 points

Mar 3, 2025 11:34 PM in response to Charles Palenz

Thanks Charles. I have repeatedly reformatted each of the hard drives I’ve gone through over the past few years to no avail. Each time I have to make room for the backup I repeatedly erase and reformat to scrub the HD clean before starting again, but Time Machine still doesn’t overwrite, and just tells me it’s full at a certain point. Different company hard drives, different sizes, always the same result. It just doesn’t work.

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User profile for user: Charles Palenz
Charles Palenz
User level: Level 2
394 points

Mar 4, 2025 8:16 AM in response to poiuytrewsdfghjk

Something is causing time machine to think the external HD is a new HD and is starting a new backup. And maybe unique to your workspace. Do the new backups begin every time the computer is turned on?


We know the time machine program works, and the OS works, just apparently not in your workspace. And with two different computers that otherwise are functioning ok. So that would seem to leave the HD or cabling which you also have changed. So the mystery. Whatever, the issue is not the OS or Time machine program themselves unless your computer has something that is modifying them.

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Time Machine - "Time Machine was only able to complete xxx% of the backup because there is insufficient free space on the backup disk."

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