Disk size of a bootable external HDD?

Discussion in 'Mac Basics and Help' started by tanventure, May 14, 2013.

  1. tanventure macrumors newbie

    Joined:
    Jan 17, 2013
    #1
    Hi

    I am thinking of making a bootable HD in case of my HD failure of my iMac with a HD of 320G, with a free space of 150G (used 170G)

    Do I need to have an external disk bigger than 320G, the size of the iMac HD, or
    larger than 170G?

    Thanks for your kind help
     
  2. Macman45 macrumors demi-god

    Macman45

    Joined:
    Jul 29, 2011
    Location:
    Somewhere Back In The Long Ago
    #2
    Basically you need enough space so that you can copy the entire Mac contents using Carbon Cloner or similar. It might be 170GB now, but it will grow...I'd go with a 500GB drive to be safe. Plenty around these days and cheap too.
     
  3. tanventure thread starter macrumors newbie

    Joined:
    Jan 17, 2013
    #3
    I have a 2TB HD as Time Machine, over 1.5TB are free, can I use it to make a bootable disk by making a partition?

    Thank you for kind help
     
  4. Macman45 macrumors demi-god

    Macman45

    Joined:
    Jul 29, 2011
    Location:
    Somewhere Back In The Long Ago
    #4
    What bus are you using? USB, FW, T/Bolt? You can in theory partition that drive and create a bootable ML copy, or clone the whole Mac ( a better option really) but It's a rule of mine that I leave TM on it's own disk without any other partitions...I use a Time Capsule which has a lot of free space, but I use it solely to backup my Imac and rMBP.

    Your call...but drives are so cheap now that buying a dedicated unit for your copy might be a better idea.
     
  5. tanventure thread starter macrumors newbie

    Joined:
    Jan 17, 2013
    #5
    Thanks for your points. BTW, what are the differences between create a bootable ML copy, or clone the whole Mac ?
     
  6. Fishrrman macrumors G4

    Joined:
    Feb 20, 2009
    #6
    If you have an iMac with a 320gb drive inside, and if about 170gb is used….

    You could get away with a partition of, say, 180gb or so -- but that doesn't leave room for "future growth" on your internal drive. Not the best solution.

    You'd probably do better by creating a backup partition of 300gb or so. Thus your backup clone can "grow" as your internal drive does.

    IMPORTANT:
    If you decide to create a partition on an existing drive to become your backup clone, I STRONGLY SUGGEST that you make it the "first" partition on the drive. If you maintain a Time Machine backup, put them on the "second" partition (or third, etc.). Keep the partitions that you want to be bootable "towards the top". Things just seem to work a little better that way.

    You can use either CarbonCopyCloner or SuperDuper to create your clones.

    Don't be intimidated by any of this. Creating that bootable backup could prove to be a lifesaver if you ever have an "I can't boot" situation with your internal drive. Just connect the backup, and you'll be booted and running again in the matter of a minute or two.
     

Share This Page