[MacTUG] Limiting Size of Time Machine backups on network drive

[Donald Duff-McCracken]

I have made these notes to myself, which I am sharing, for interest and critique ;-)

 This is how I am limiting the file size of backups on a network drive. It seems to work fine, and stops the backup from growing past the desired size (deleting the old backups as one would expect)…

don
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If you are having more than one Mac backup to one network volume, one of the 'more greedy' macs can quickly steal all the space on the volume. One solution is to partition the network drive into as many partitions as you have Macs that you want to back up, but that is not very efficient.

Another solution is to limit the size of the spare bundle image that Time Machine uses to back up to when it is using a network drive. Here are the steps:

  1.  Create the disk image: In Disk Utility create a disk image where:
     *   The 'Save As' name is 'computer name_macaddress' -- e.g. 'freds computer_A001d544532c2'
        *   if your computer name has a space in it, leave the space
        *   Keep name case sensitive (just in case)
        *   You can add the file extension '.sparsebundle' (e.g. 'freds computer_A001d544532c2.sparsebundle'), but this is not required as it is added when you choose the Image Format (a few steps down)
     *   The "Name" is "Backup of computer name" e.g. "Backup of freds computer"
     *   The size is the max desired size
     *   The format is 'Mac OS Extended (Case-sensitive, Journaled)'
     *   The Encryption is 'None'
     *   Partitions is 'Single Partition – Apple Partition Map'
     *   Image Format is 'sparse bundle disk image'
  2.  Copy it to the Network Volume that you are using for Time Machine (I will assume that this Network Share is already configured for Time Machine), or just save it there.
  3.  Tell Time Machine to backup to that network volume
  4.  A warning message may appear warning you that you are backing up to a sparsebundleimage that Time Machine is not certain about. Disregard this message, Time Machine is just fretting ;-) It may also go through a verTime Machine will slightly rename the sparsebundleimage by removing the MAC address in the name of the disk image, for example 'freds computer_A001d544532c2.sparsebundle' will change to 'freds computer.sparsebundle'

A few notes:

  1.  It seems that one needs to create the sparse bundle image as described in the above instructions. (versus merely resizing the Time Machine one in Disk Utility).
  2.  Similarly, if the fixed size disk image gets too small, it seems that it is difficult to resize it. Some people build a new disk image of the new desired size and copy the contents of the old time machine into the new disk image. This seems excessive, I would just stash the old backup for a while (as a safeguard), create the new backup (of the new size) and start over.

Here are some good links:
http://hints.macworld.com/article.php?story=20071108020121567
http://code.stephenmorley.org/articles/time-machine-on-a-network-drive/
http://www.youtube.com/watch?v=9y41brrCffY
http://superuser.com/questions/300741/time-machine-not-recognizing-sparsebundle

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