Time Machine with two drives?

Discussion in 'Mac Basics and Help' started by macstatic, Dec 21, 2010.

  1. macstatic macrumors 65816


    Oct 21, 2005
    I've looked up a few threads on the subject but found no definite answer...

    I'm wondering if using two separate external Firewire hard drives for backing up an iMac with the aid of Time Machine will work and be safe (not messing up things etc.)?
    One external drive is now attached to the iMac, backing things up every 3 hours (I found the default hourly backup a bit too much so I installed Time Machine editor in order to change this). It works just the way it should.

    But in case of theft, fire etc. it would be nice to have yet another backup drive as well. Naturally that drive would be stored in an off-site location and thus not backed up to that often, but at least I wouldn't lose absolutely all my files if my computer + regular backup drive was to be stolen or damaged in a fire, just the very latest files.
    So let's say I pull out that drive every 2 weeks or so, disconnect the regular Time Machine drive, attach the "off-site stored drive" and tell Time Machine to do a backup right away. Would my computer be able to tell the two drives apart (I'd give them different names of course), understanding that the "regular" backup drive should just continue backing up as it left off last time, or will it get confused?

    I like Time Machine because it's maintenance-free, so I'd rather not use some other, separate and complicated backup software for the "off-site" drive if I can avoid it.

    By the way: my backup drive is a 2.5" external Firewire drive which means that it takes its power from the Firewire 800 cable totally eliminating any additional power supply and cables. Just one cable and a small enclosure.
    Neat and tidy and very much recommended!
  2. simsaladimbamba

    Nov 28, 2010
    Try CarbonCopyCloner or SuperDuper and clone the TM HDD to that other HDD, but TM will not backup to two HDDs.
  3. pomme4moi macrumors newbie

    Dec 6, 2010
    I know you don't want to use other back-up software, but you should if your data is important. Just as two different back-up drives protect against a single drive failure, two different back-up software products protect against a single software product failure. No matter how good Time Machine or any other product is, you never know when a bug will be introduced in a new version. And you won't know until you try to recover your data …
  4. mynameismary macrumors newbie

    Dec 20, 2010
    East Tennessee
    Even if you plug them up separately - as in use one, unplug it, use the other, unplug that one...

    Just asking. :)
  5. mstrze macrumors 68000

    Nov 6, 2009
    Nope...TM will only backup to one location. It can backup multiple sources/drives (I back up my internal and my external iTunes drive), but only TO one HDD.

    If you remove the drive it will ask where it is and only run once you put the original drive back, or specify a new backup drive. I suppose you can specifiy a 'new' backup drive each time, but it will perform a complete backup of the entire drive each and every time (several hours for most of us). It will not be able to do the incremental backups as designed.
  6. mstrze macrumors 68000

    Nov 6, 2009
    Just wondering: How is every hour (for a process that runs in the background and is hardly noticed by me) too much, yet every 3 hours is just fine? Instead of writing a small file every hour, you are accessing the TM disc and writing a file 3 times the size for 3 times as long.

    I guess I have never been worried one bit about TM running every hour. I would think it would help me if a drive crashed or a project got corrupted while I was working on it and I would have lost only a maximum of 59 minutes of work...MUCH better than losing 2hrs 59 minutes of work. After working on iMovie projects for hours and losing 8 hours of work by a file corruption, even 15-minute backups sound great!

    Just something that has been bugging me for a while. I'm just not sure what the theory behind making backups less frequent. I'd love to hear your thoughts.
  7. Tumbleweed666, Dec 22, 2010
    Last edited: Dec 23, 2010

    Tumbleweed666 macrumors 68000


    Mar 20, 2009
    Near London, UK.
    Agreeing with previous posts re these points
    1) How can every hour be too often, its in the background, how can you notice?
    2) Backup using two different methods, otherwise, say there is a TM bug or TM for whatever reason doesn't back something up (maybe you missed a folder?) , you have effectively only one, useless backup. Better to have a complete different source to go to.

    I do 3 backups - TM (hourly), once a week online, infrequent when I remember, should be more often , must do one tonight, CCC to another local drive.
  8. RedTomato macrumors 68040


    Mar 4, 2005
    .. London ..
    I used to do this.

    I had a TC at home, and at my old job had another TC. In Time Machine Preferences, I just set it to use whichever TC I'm currently connected to.


    - 1st backup at work taking longer than a working day. Solved by excluding some folders and re-adding them later, and by directly connecting to the TC instead of via wifi.

    - Having to remember to manually tell my laptop to start using a different TC. Solved by only changing over on a weekly basis i.e. backing up to the home TC one week, and backing up to the work TC the next week.

    I looked into configuring an Automator action to do it automatically, but never got round to building one before I stopped working. Marco Polo is also good for location-based actions, but doesn't (yet) change TM drives based on locations.

    You could do the same by just having two external drives for TM, and keeping one off-site and changing the two drives over every now and then. The two drives need to have different names, and TM will need to do a file survey each time you tell it to use a different drive, which can take a while, but overall it's really easy do to, and very worthwhile.

    There are various hacks out there to 'trick' TM into thinking it's backing up to the same drive when it's really backing up to a different drive, but I *really* *really* wouldn't touch them. Just do everything above board, through the TM prefs pane and you should be fine.

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