Backing up an External HDD to Time Machine

Discussion in 'macOS' started by nuck, Apr 28, 2018.

  1. nuck macrumors newbie

    Sep 5, 2008
    Question.. I have set up an external hard drive ("Hard Drive A") to backup to my Time Machine external hard drive ("Hard Drive B"), but I cannot figure out how to view the backups unless that external hard drive (A) is plugged in.

    For example:

    If Hard drive A is plugged in, and I go to "Enter Time Machine" I can see Hard drive A listed under devices in the backup and see the files.

    If Hard drive A is NOT plugged in and I "Enter Time Machine" I can't see Hard drive A listed and can't access the files.

    Does anyone know how to view these files? If I need Hard Drive A to be working and plugged in to access it then the whole backup is worthless since the whole point is to back things up to Hard Drive B (Time Machine) in case hard drive A stops working.

  2. komatsu macrumors 6502

    Sep 19, 2010
    I might be wrong about this but I think Time Machine is primarily designed to backup your Mac's internal HDD but I'm sure some other people will have some other input on this.
  3. MC6800, Apr 30, 2018
    Last edited: Apr 30, 2018

    MC6800 macrumors 6502

    Jun 29, 2016
    If A dies you could theoretically replace it with a new drive and restore its Time Machine contents from B. But normally you wouldn't do it that way: for redundancy you would have both A and B backing up the same Mac drive(s).

    In any event, the contents of an unencrypted Time Machine backup is a set of folders, one per backup event, that are just as readable as the original drive. They use hard links to make one actual file appear in multiple folders without taking extra space if it didn't change.
  4. chabig macrumors 603

    Sep 6, 2002
    I would discourage you from backing up your Time Machine drive. Instead, just add the second drive to your Time Machine settings and the Mac will alternately use both drives. That way you have two independent backups. You can even rotate them--store one offsite and swap them out every week/two weeks/four weeks, whatever is convenient for you.
  5. Fishrrman macrumors P6


    Feb 20, 2009
    Instead of creating a second TM backup, I suggest that you download either CarbonCopyCloner or SuperDuper (both are FREE to download and try for 30 days).

    Then, create a bootable cloned backup on your second external drive.

    Now you'll have both a TM backup AND a bootable cloned backup.

    Give either CCC or SD a try.
    If you don't care for them, you can always just erase the external backup and start over.
  6. chabig macrumors 603

    Sep 6, 2002
    That is also an excellent idea.
  7. nuck thread starter macrumors newbie

    Sep 5, 2008
    This is fantastic. Thanks everyone!

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