ext hdd and time machine

Discussion in 'iMac' started by halfmonkey, Jan 19, 2013.

  1. halfmonkey macrumors regular

    May 17, 2011
    I currently have a 1tb iMac and I'm looking into getting an ext thunderbolt connected hdd. Before I buy, I'm hoping someone can clarify for me some questions.

    If my iMac is 1tb, do I buy 1tb hdd or maybe 2tb or 3tb? The reason why I ask is, let's I currently have 500gb of data on my iMac. Of course, the first back will 500gb, half, if I were to buy a 1tb ext hdd. So my question is, on the second back up assuming no changes and still at 500gb, does Time Machine write another 500gb to the ext hdd so now a total 1tb of back up data? Then, if (assuming no changes), it's time for another back up and it writes another 500gb, will it over write the first 500gb?

    If it doesn't work like this, can someone explain how and what data TM actually writes so I know if I can stick with 1tb or if I should get 2 or maybe 3 tb ext hdd?

    Also, if I do back up to TM and let's say i sell me computer, am I able to use the TM back up to migrate all of my files (word files, photos, videos, excel files, etc) to the new computer by connecting the ext hdd and "restoring" the new computer with the TM back up information?
  2. duri macrumors member


    Jan 19, 2013
    Rothrist, Switzerland
    TM uses incremental backups

    TM creates incremental backups. So the first Backup will use a lot of space, the next one just will add the changes to it. Once your ext. TM Volume is full, TM will start to automatically (asking you before) erase the oldest backups you have got.

    To restore from TM backup, just start ur Mac from recovery (press cmd + R while booting) . There you can choose to recover from TM.
  3. halfmonkey thread starter macrumors regular

    May 17, 2011
    Yes, I understand that is what you would on your existing computer if something were to happen but is this what you would do if you were to buy a brand new computer and actually want to transfer your docs, music, photos, videos, apps, settings over? Can you do that with a TM back up?
  4. WilliamG macrumors G3

    Mar 29, 2008
    If you buy a new computer, you can just mount the Time Machine backup image, and go to the dated folder of the backup you want, or to the latest folder, called - handily - "Latest," and then just copy files manually across. You don't need to do full restore at all. It's there if you need to, but you can either use the snazzy Time Machine interface to restore individual files (which in my mind takes too long), or just do it manually, which is also very simple. Either way, it's easy to restore individual files and folders and not the whole backup (OS etc). You wouldn't want to do that anyway if you bought a new machine since the drivers etc for the graphics card etc may not be there on your backup.
  5. duri macrumors member


    Jan 19, 2013
    Rothrist, Switzerland
    The 3th Option is to use Migration Assistant with ur TM backup. Start Migration Assistant on your new Mac and choose to migrate the files you like from the TM backup. This way, you just migrate your user account and your files and settings over.

    But its still "cleaner" if you do it all manually by hand without the Migration Assistant.
  6. Dr FranknFurter macrumors member

    Mar 23, 2012
    Cambridge UK
    Hi, i've just received my 2012 iMac and did exactly as above. Used Migration Assistant to move my Apps, Files and User accounts from my Time Capsule (whick is where time machine backs up to) some people find it cleaner to do a new install but my Time Capsule data is only a few old from my newish Air so i'm confident it was a clean install.

    The only issue I have and someone here can no doubt help, is my iTunes Media is stored on an external USB3 HD (backed uo to Time Machine as well) I expected this to be copied over but it appears the Index has copied but not the Media. Obviously it has mirrored the Macbook Air and not the External which I guess is normal but I didn't have time to check the external whould provide the media to the iMac or how to copy the media onto the iMac.
  7. Bear macrumors G3

    Jul 23, 2002
    Sol III - Terra
    The exact size is a tough call, it depends on how much changes on your computer on average every day. At the very least I would recommend at least 2 TB drive so if your 1 TB fills up you still have room for multiple backups. And also the last time I checked, the price differences between 1 and 2 TB and between 2 TB and 3 TB wasn't that much, so it doesn't really make sense to get a 1 TB drive at all. And it might make sense to get a 3 TB drive for TM.

    You wouldn't actually want to do a TM restore as the OS may not have the drivers needed for a new computer. However, when you first start up a new system, it asks if you want to import from a TM backup. Or you can do so after the fact with Migration Assistant.
  8. Fishrrman macrumors G5


    Feb 20, 2009
    "If my iMac is 1tb, do I buy 1tb hdd or maybe 2tb or 3tb?"

    My suggestion.

    DON'T rely on Time Machine as your only backup.

    You need a "bootable external backup" as well. If you ever have one of those "it won't start up" moments, having an easy second way to boot is invaluable. There's only so much you can do with a recovery partition.

    You might consider a 2tb drive. Create one partition of, say, 750gb (make it the first partition), and the second one can be what's left.

    Use CarbonCopyCloner to create a bootable clone backup on the first (smaller) partition, and use Time Machine on the other partition.

    In a "moment of extreme need", having that bootable backup will run circles around Time Machine...

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