Using Multiple Drives with Time Machine

Discussion in 'Mac Accessories' started by imfrog2002, Mar 16, 2008.

  1. imfrog2002 macrumors 6502

    Oct 20, 2007
    Okay, I'm sure this has been posted SOMEWHERE before, but I can't find it. I was wondering if you can use more than 1 External HDD with time machine? I have 2 500GB drives, and I have one that I use right now, but I'd like to use the other one for secondary backups, as in the ones that would be deleted when the first disk fills up. Is there a way to do that? Thanks in advance!
  2. balk macrumors member

    Mar 5, 2008
    Due to the nature of Time Machine* you cannot extend a backup over two physical drives, unless you use a RAID 0 setup. You can however start with a new, empty backup drive until it's full, clean the first one and start over again.

    *) Time Machine uses hardlinks to create a full backup every time you make a backup without copying your whole system every time. Some explanation Hard links cannot span over two drives so a full initial backup is required the moment you change drives.
  3. Schroedinger macrumors regular


    Feb 12, 2004
    Baltimore, MD
    As I am swimming in internal storage and back up needs, I actually use time machine with 5 external drives concatenated together. You can combine both of your externals into a 1 TB concatenated drive and and Time Machine will back up to the entire 1 TB.

    You will unfortunately have to lose the back ups you have to this point, but going forward you'll have back ups forever. Of course I must also point out that you run the risk of losing everything if either drive fails, but this is a back up solution so in the case that happens you you can replace the drive and back up from there forward.

    In case you don't know what concatenation is, it is an option under disk utility. It combines all the drives into one volume and keeps all the space. It isn't safer than raid, but it is easier.
  4. balk macrumors member

    Mar 5, 2008
    Be careful with this, because
    "Be sure to back up your data frequently. If any one of the drives is damaged, you will lose the data that’s on all the drives." - Concat manual.

    Same holds for RAID0
  5. imfrog2002 thread starter macrumors 6502

    Oct 20, 2007
    Thanks for letting me know. The secondary drive is iffy. It's gone down 3 times before, so I'm just going to stick with my current setup, and use the extra space for non-important stuff. :) Thanks!

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