Two Macs, One Backup Storage Device?

Discussion in 'Mac OS X System & Mac Software' started by bowjest, Nov 4, 2009.

  1. bowjest

    bowjest Registered

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    I've been using a Lacie terabyte drive for the last couple of months to backup data on one of our Macs.

    My wife now has a new MBP and I'd like to know if I can backup data from both our existing MBP as well as her new MBP or will I need to get a separate backup drive for the new Mac?

    I'm afraid to plug in the new MBP for fear that it will prompt the Lacie drive to reformat itself.

    Thanks in advance for your help.
     
  2. ElDiabloConCaca

    ElDiabloConCaca U.S.D.A. Prime

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    Nothing in either of your Macs would automatically format a disk without informing you first and presenting you with the option of cancelling said action.

    Yes, you can use a single disk to back up two Macs, given that they do not share a common computer name.

    http://forums.macrumors.com/showthread.php?t=405606

    Be aware that if you have a multi-interface external drive (one with USB, eSATA, FW400 and FW800 or some combination therein) that the drive can only be hooked up to one computer at a time. You can't "get tricky with it" and connect the MBP to the USB port and the other computer to a FireWire port -- they don't work that way -- so you'll have to keep drive use independent and mutually exclusive between the computers.

    A typical backup procedure would look something like this:

    1) Connect Time Machine disk to computer 1 via USB/Firewire/eSATA.
    2) Time Machine does its thing.
    3) Properly unmount/eject the Time Machine disk from computer 1
    4) Connect Time Machine disk to computer 2 via USB/Firewire/eSATA
    5) Time Machine does its thing.
    6) Properly unmount/eject the Time Machine disk from computer 2
    7) Repeat until your wife stops you
     
  3. bowjest

    bowjest Registered

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    Thanks, Diablo,

    So, just to confirm, if I attach the new MBP via firewire like I do now with our family MBP, I can backup data to the same device (albeit not at the same time as the 15" MBP) without worrying that the data from the 13" MBP is going to overwrite the existing 15" machine's backups?
     
  4. ElDiabloConCaca

    ElDiabloConCaca U.S.D.A. Prime

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    Yes.

    If you use the Finder to browse the Time Machine backup disk, you'll see that there is a single folder at the root of the drive entitled "Backups.backupdb". If you open that folder, you should see another single folder that's titled with the name of your family MBP.

    If you elect to use this disk with another Mac, then Time Machine will simply create another folder alongside the existing computer-named folder with the new computer's name, and it will keep all backups related to that machine inside of that folder -- segregated, mutually exclusive, and "invisible" to the other MBP. Essentially, each computer will have its own folder for backups.

    You can see where two computers named the same thing would screw this process up -- they would each point to the same folder. Before continuing, ensure that each machine has a unique name.

    Simply plug the drive into the new MBP, and you'll be prompted with a dialog box that asks if you want to use the drive you just connected as a Time Machine backup drive. Say "yes," and you're off to the races.

    Oh, I haven't tried this personally, but I would believe that you would need at least as much free space on the Time Machine drive as the size of the data on the new computer to be backed up initially, for the first Time Machine backup.
     

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