Can a single External HDD be used for Time Machine and to also hold an Image copy?

Discussion in 'macOS' started by Libertine Lush, May 8, 2010.

  1. Libertine Lush macrumors 6502a

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    Nov 23, 2009
    #1
    I may upgrade my MBP with a Hitachi HDD and I'm curious to know if it's possible to use my Western Digital external HDD to act as both the Time Machine drive and also store an Image of the MBP's HDD, using oft recommended freeware like Super Duper or Carbon Copy Cloner?

    If it is possible, I assume I would have to first set up the drive as the Time Machine drive, since I recall it initially asks for you to format it. Then proceed to placing an Image copy on it.

    I've never made an Image before; I merely understand it's an exact replica of your HDD. So should the MBP's internal HDD fail one day, I could hook up my WD external and proceed to recover the image on it? (However that is done; hopefully I'll never need to know.)

    Thank you everyone.
     
  2. Xenc macrumors 6502a

    Xenc

    Joined:
    May 8, 2010
    Location:
    London, England
    #2
    Time Machine backups appear as a single "sparse bundle" file on the selected backup drive. Storing other files on the drive will not prevent Time Machine from backing up your computer.

    Note that OSX is able to import a Time Machine backup during installation to "recreate" your computer should disaster ever strike. You can also import a Time Machine backup through the Migration Assistant application.
     
  3. old-wiz macrumors G3

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    #3
    The safest way to do this is to partition the external drive into 2 partitions; one for time machine and one for superduper/CCC. SuperDuper/CCC can create bootable copies so you can easily recover without taking time to restore from time machine. there are lots of posts on this in the forums. SuperDuper doesn't usually create an "image" as in .dmg, but rather clones the HD into an exact copy that is bootable.
     
  4. Libertine Lush thread starter macrumors 6502a

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    Nov 23, 2009
    #4
    Thanks. Great to know.

    I learned through these forums some months back, that while transferring all data that way works fine for most, if you're more particular, programs should be installed anew, as importing or using Migration Assistant (I forget which, or maybe both) results in carrying over some excess of files. Basically, I recall people were saying the install would not be as clean. For that reason, I rather clone my HDD, which from what little I know, poses no disadvantages.

    A bootable copy means that when you turn on the computer with the HDD attached, it will recognize the HDD to use it to load OSX? So is that to say that not partitioning an external into 2 partitions if I wish to create an image backup makes the resulting external it of little use?

    Did I use the term "image" incorrectly? I barely understand enough so to phrase this thread's initial question. I thought cloning basically meant making an image backup.
     
  5. old-wiz macrumors G3

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    #5
    Look at it this way:
    Suppose you have a 1000 gb external drive and a 320 gb internal drive. You first make a clone with SuperDuper, and it uses up, say, 200 gb, leaving 800 gb. Now you start time machine, and it starts to use up that 800 gb. Eventually time machine will fill the remaining space completely. Then if you try to make another clone with superduper, it will fail cause there will not be enough space since time machine gobbled it up.

    If you partition it into 1 320 gb (for superduper) and 1 of the rest (for time machine) you will always be able to do a clone via superduper and time machine will only use its own space.

    When you boot with the option you get presented with a menu of available bootable volumes, so you would just pick the clone volume and there you go.

    Using Time machine to restore is fine, but if you have a superduper clone you can immediately recover from a failed internal drive since you have a copy on the external. If you then replace the internal HD you can copy the clone back a good deal faster than if you used time machine to restore it.
     
  6. Ash9414 macrumors 6502

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  7. Libertine Lush thread starter macrumors 6502a

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    Nov 23, 2009
    #7
    Ah! I had overlooked that while a Time Machine backup provides protection from data loss, it is unworkable until you replace a failed internal with a new one. Seems self-evident now. Thank you, old-wiz. Got a much better basic understanding of this now.
     
  8. old-wiz macrumors G3

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    Mar 26, 2008
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  9. Libertine Lush thread starter macrumors 6502a

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    Nov 23, 2009
    #9
    old-wiz, I was just thinking over what you wrote, and there's one thing I'd like to insure I understand correctly. Is this statement true?: If my internal HDD fails and I partitioned my WD external separately for Time Machine and the cloned copy, when I turn on the MBP with the WD attached, a menu will appear and it will know to ignore the Time Machine partition and display only the clone partition; however, if this WD isn't partitioned, no menu would show or if it does, it would be blank as it can't recognize/locate the clone copy on the HDD when it's not in it's own partition?
     
  10. old-wiz macrumors G3

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    Mar 26, 2008
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    West Suburban Boston Ma
    #10
    In case the internal HD fails, you need to hold down the option key (I think - its one of the control keys) and then you will get a menu for where to boot from. It will show all bootable volumes or partitions. I'm not sure what will happen if SuperDuper shares the partition with time machine.
     
  11. Libertine Lush thread starter macrumors 6502a

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    Nov 23, 2009
    #11
    Thank you again, old-wiz. I'll do some more searching around then before I post a separate thread for this question.
     

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