APFS Volumes + Time Machine

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APFS Volumes + Time Machine

I have a 500GB external drive. Using Disk Utility, I created two APFS volumes on the drive, which I will call A and B. I created volume A with a reserve of 100GB and a quota of 100GB. I then created volume B with a reserve of 400GB and a quota of 400GB. Note that both volumes are formatted as APFS encrypted. So far, so good. Still in Disk Utility, I can see that each volume shows its respective quota capacity and available capacity.

Now, I want to use volume A with TimeMachine. When I open TimeMachine and select volume A as my destination drive, it asks me to enter an encryption passcode. I do this, and TimeMachine finishes preparing the volume. When I now look in Disk Utility, however, volumes A and B both show an available capacity of 500GB. It seems like TimeMachine removed the specified volume sizes, and is treating the entire disk as available to TimeMachine.

Using APFS volumes (or, if necessary, APFS partitions), how can I reserve a portion of my external drive for Time Machine backups, without exceeding a specified threshold (in this case, 100GB)?

iMac Line (2012 and Later)

Posted on Nov 29, 2020 3:32 PM

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Answer 1

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Barney-15E

Level 10

117,436 points

Nov 29, 2020 3:52 PM in response to pomme4moi

That's what Time Machine wants to do. It wants the entire disk. It doesn't like to share.

If you want to split up the drive, Partition it. I think that will make Time Machine leave the rest alone.

What are you backing up that only uses about 30GB? 100GB can't backup up much more that about 30GB of data.

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Answer 2

pomme4moi Author

Level 2

167 points

Nov 30, 2020 10:03 AM in response to Barney-15E

Thank you Barney. I did another test, this time partitioning the one physical disk into two APFS partitions. And this time, TimeMachine recognized the 100GB partition and operated within the partition. So you were correct, this is the way to go if I want to have TimeMachine backups and other data on the same physical drive.

Re your other point, my external drive has a much larger capacity. I was just using 500GB as an example.

Thanks for your help. Much appreciated.

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APFS Volumes + Time Machine

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