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  • #4002384

    Time Machine Backups of External Drives When Changing Macs


    by j1inha ·


    Good day to you all –

    I have been running an M1 iMac with a 4TB external SSD being used as direct access storage, and I use Time Machine to back up that external SSD to two external 5TB HDDs once a month. I don’t even backup the Mac’s internal SSD, just the external SSD where I keep all my data.

    I am switching now to a 16″ MacBook Pro (M1 Pro) and am wondering:

    Is it possible for my MB Pro to pick up where my iMac left off with the TM backups? Or do I need to wipe the two HDD backup drives and re-initiate the TM backups of the 4TB SSD through TM on the new MacBook? It would stink if every time you bought a new Mac, you had re-do several TBs of backups like this.

    Thanks for your help!

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    • #4002392
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      I’m going with no.

      by rproffitt ·

      In reply to Time Machine Backups of External Drives When Changing Macs does use Time Machine to transfer your stuff and more but I’ve yet to find an Apple OS user to move a TM drive and carry on.

      After the new computer has your stuff, make a new Time Machine drive and let it work.

    • #4002416
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      I’m going with Possibly

      by mrmacfixit ·

      In reply to Time Machine Backups of External Drives When Changing Macs

      As you are not backing up the Internal Drive of the existing iMac, then there is no Index for it in the Time Machine preferences.
      There is however, an index for the the external 4TB SSD on the 5TB HDDs

      Assuming that you intend to NOT backup the internal drive of the MBP, and you make sure that the Time Machine preferences match what you had on the iMac, there is a possibility that TM will recognize that the ID/contents of the 4TB match the backups it already has stored and just carry on as normal.

      Failing that, TM will start afresh and copy the 4TB contents to the 5TB drives as a NEW archive. Nothing would be lost in either case.
      I don’t see a need to reformat the 5TB drives.


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