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Mountain Lion includes a feature to configure multiple Time Machine locations and to back up to those locations when they become available (plugged in external drives, accessible network drives, etc). Can 10.8 or any older version of OSX, possibly including third party software, be configured to back up different data to different locations?

Use case: I have 100GB of storage available on a cloud storage server, and a 250GB external hard drive. I want everything on my computer except media (photos, videos, music) backed up to both of those locations. I have another much larger drive that is accessible less often that I keep backups of my media on. Currently I have Time Machine configured with an exception list for the media locations and it backs up to all three drives (dumbly in 10.7, but smartly when I upgrade to 10.8) and then I manually make a backup of all the media directories using rsync occasionally. I would love for the media backup to be automatic when I plug in the large drive.

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  • Are you OK with backing up using two different OS X user accounts?
    – Global nomad
    Feb 7, 2013 at 22:16
  • @Globalnomad I'd have to give both accounts access to all the files in question, but that's not a huge hurdle, so feel free to submit an answer that has that requirement.
    – Sparr
    Feb 7, 2013 at 22:21
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    Short of scripting the changes to the exclusions and triggering them when the "media" drive gets mounted (which is theoretically possible) - the built in backup scheme is designed for one set of exclusions to rotate backups between two drives (if configured).
    – bmike ♦
    Feb 7, 2013 at 23:10
  • @Globalnomad you could undelete your answer and flesh out how things work. Each user can add exclusions for themselves and have both backups contain the same rules. Sometimes a detailed no answer works well...
    – bmike ♦
    Feb 7, 2013 at 23:12
  • Done. I've added a note so even though I misunderstood the question rendering my answer incorrect. Hopefully it'll eliminate one dead end from being explored by others searching for an answer.
    – Global nomad
    Feb 7, 2013 at 23:18

1 Answer 1

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The short answer is no, but here is why and how the exclusions work when you pick different rules for two accounts.

Whether you have one backup destination or two, the rules for multiple users is to combine the exclusions for each user with the exclusions from the system so that each user can exclude different things, but there is no "inclusion" mechanism to add something back that another user has denied.

There is a nice article on having multiple users and goes into more details on setting up multiple exclusion lists:

It's not going to save backup time or space as you asked, but perhaps drives can get larger and you could just have both drives hold the same content since incremental updates mean that unless a file changes, it only gets copied once to each destination, speeding backups for subsequent backups to each individual drive when it's connected.

Pulling one drive from rotation with two works well as the system just carries on with the drive connected and then when the further out of date drive mounts again, one of the next two backups will catch it up with all changes since it was last mounted during a backup.

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  • Is having them both logged in only relevant to the backup happening automatically when the drive is plugged in?
    – Sparr
    Feb 7, 2013 at 22:28
  • Yes. else Time Machine won't run for the user account that was logged out.
    – Global nomad
    Feb 7, 2013 at 22:30
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    Time machine runs as a privileged system user (basically root) all system files, user files, and user exclusion lists get reconciled at the moment backupd gets launched and goes to work. You can use the command tmutil isexcluded from a shell as root (sudo -s) or two shells - one as user a and one as user b to convince yourself that a file is either in or out at any one time - no matter what user is or is not logged in when the backup commences. tmutil compare is also useful to show which files will be included when the next backup event starts.
    – bmike ♦
    Feb 7, 2013 at 22:44
  • This solution would not allow one user to browse all of the backed up files on the large drive, only one or the other sets (media or non-media) at once?
    – Sparr
    Feb 7, 2013 at 22:55
  • bmike, I set up my Mac (two users, different backup destinations) using info from pondini.org/TM/10.html. You're correct, I misunderstood the original question.
    – Global nomad
    Feb 7, 2013 at 22:55

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