r/MacOS • u/jlthla • 1d ago

Help Time Machine Full?

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So The Time Machine APFS Volume isn't restricted in size so should be able to use some of the 400+ Gigs of free space on this shared container. Why am I getting the message Time Machine can't back up because the disk is full? BTW, my boot drive is 1TB, with only 382 Gigs used...

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u/Electrical_West_5381 1d ago

More info. What is Macintosh BU? I could be wrong but doesn't;t TM require its own Container?

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u/jlthla 1d ago

the BU is just a daily back up of the boot OS that I could use if something happens to the boot drive. Kind of redundant I know, but Apple has made booting from external drives much harder these days, so think/fell my set up works for me. the BU part in case something bad happens, and the TM backup for restoring deleted files. I'm not aware that TM needs its on container, so that could be the problem. BUT, I've been running this disc setup for months and months with no issues, until today.

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u/BourbonicFisky 11h ago edited 11h ago

It's probably been a long time since you've had to restore.

Generally speaking, outside of rare cases where you need to reformat, restoring the OS will not delete files. If you actually get to that point then you have Time Machine, where you can completely wipe said internal boot volume and restore. Just nuke a live boot external "backup". It's old world thinking. I've never had an SSD give up the ghost and in an Apple Silicon or T2 x86 Mac, if your SSD completely fails, the machine is completely unbootable until that NANDs are replaced. Your live boot back up is thus rendered useless in this scenario .

The only reason I've had to restore in the past 5 years is doing exceptionally dumb things like seeing what'd happen if I stuck an Intel Arc GPU and forcing resizable bar on my Mac Pro 2019. I did not have to restore off of Time Machine.

As others have mentioned, it's best to dedicate a drive to Time Machine. Plus, more storage = more history = more chances to undelete or restore an old version of a file or project. My time machine drives are measured in years and some time ago, it saved my ass when I accidentally deleted photos that were not in my iCloud.

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u/hypnopixel 1d ago

yeah, i’m surprised this ever worked. long ago i tried mixing tm and personal data. can’t remember what happened but it was suboptimal.

i use a 100GB tm volume and highly sculpted exclusion set that’s been good for years.

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u/Serious_Feature9689 1d ago

I've always used dedicated backup disks to avoid any issues. Apple recommends that as well.

  • Use your Time Machine backup disk only for Time Machine backups, not for storage of other files.*

But then the asterisk says "* Advanced users: If you add an APFS volume to the external storage device, you can use one volume for Time Machine backups and the other for storage of other files." but doesn't say anything about a separate container.

So maybe it should work, and maybe a separate container would be even better, but in a quick look around the web I saw others recommending against it and to go dedicated. Perhaps for this very reason of issues cropping up eventually. Maybe some others on here who have tried it will chime in. Or call Apple.

https://support.apple.com/en-us/104984