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datwinz Author

Level 1

23 points

Transfering time machine backups to another drive

I recently learned that Big Sur supports APFS for time machine backups and not only that, it is faster aswell. Now according to this Apple support page I should just erase my disk and start from scratch. But I don't want to do that, I like having access to my older data if necessary.

My plan is: transfer the backups to another drive, reformat the first drive for APFS time machine backups and transfer it all back. Here is were my problem starts. I could try to use the built-in copy functionality of MacOS, but that isn't great for a large amount of files. Namely, if something goes wrong, it deletes your progress and you have to start all over again. So I tried to find an alternative:

I tried Teracopy. That is an app that makes a file list to copy and if something goes wrong, it just goes to the next file and tries again later. But because of the large amount of files (14,000,000), it crashes while making the file list.
I tried using Carbon Copy Cloner, but that just said it couldn't clone time machine drives.
Then I tried using rsync. That is a terminal utility with, for this usecase, the same functionality as Teracopy and I let that run last night. I have 44 time machine backups, 800GB total, and it copied seven of them. But for some reason those seven totaled 850GB. I only have a 1TB drive, so that wouldn't really work either.

I don't really know what to do now, does anyone have a solution?

MacBook Pro 15″, macOS 11.2

Posted on Feb 19, 2021 5:00 AM

Top-ranking reply

Barney-15E

Level 10

115,954 points

Posted on Feb 19, 2021 5:36 AM

You can no longer copy a Big Sur Time Machine backup, so it may not inherit one after copying, either.

Why do you not want to erase and start over? What older data do you want to have access?

There is no guarantee that "older data" which you erased from your Mac will still exist on your backup. It doesn't start deleting those things until it starts needing the space, but there is still no guarantee that it will maintain those deleted items. It is not an Archival backup. It maintains them for a while, but will eventually delete them.

If you want to keep them, remove the drive from Time Machine and start over on a new drive.

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Transfering time machine backups to another drive

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