When does Time Machine become full?

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When does Time Machine become full?

"The oldest backups are deleted when your disk becomes full."

How exactly does this happen? The oldest backup is the largest and others are incremental. So does it mean the SECOND oldest backup is the first to be deleted?

And wouldn't the storage be inefficient by then anyway? For example, I have a 2TB device and my incremental backups are typically <20GB. So does that mean the external device will be >99% full before an old backup is deleted? Isn't 99% full already way past the efficiency of read/write?

I'm presently at 44% empty space so I'm not worried, but I am curious.

Previous questions on this topic seem to be deflected by Apple or highly rated users as "get another device" which doesn't answer the basic questions about deletion. Thanks.

Mac mini, macOS 10.14

Posted on Dec 23, 2021 10:46 AM

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Answer 1

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muguy

Level 10

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Dec 23, 2021 10:54 AM in response to martindo123

The disc becomes full when it cannot make a future backup based on space required and swap file space; that will vary. I had a 4TB backup disc and it was often full at around 95 percent of space (I never paid that much attention). I have yet to even come close on my 12 TB backup drive.

The oldest backup is indeed deleted; just like weekly backups are rolled into monthly backups, the same happens. The files that fall off are old changes and deleted files. Files that haven't changed are untouched as is the most recent version of a file with changes.

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When does Time Machine become full?

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