I have recently started using Time Machine to backup my Mac and love knowing that I can, not only do a full system restore, but a full system restore to almost any point in time!

Time Machine fairly intelligently takes a full copy of your system the first time you perform a backup and then incrementally adds new/modified files on each subsequent run.

The first thing I noticed was my incremental backups were rather large 20GB+. Which, over wireless takes a really long time and will soon fill up my fileserver. Surely I’ve not added/modified 20GB worth of data in an hour? Well, no- I haven’t but I run VirtualBox which reads/writes to a virtual hard disk image of roughly 20GB- so even a single 1KB file modification will cause Time Machine to backup the entire virtual hard disk.

This is easily fixed- by opening up Time Machine preferences, clicking options and adding ~/VirtualBox Vms to the exclusions list. I also chose to exclude a few more paths after a little more research:

My incremental backups are now normally under 100MB and I use a different backup tool on my virtual machines.

I may decide to add my outlook mailbox to the exclusion list going forward as I’m connected to an exchange server (all the data is stored on the server). Time Machine backs up the entire mailbox every time as it is stored in a single file.

And finally, the default behaviour of Time Machine backing up once every hour seems a little excessive (although I’m often travelling and not connected to my network so the backups are skipped anyway). I was quite surprised not to find any configuration options within the Time Machine preferences but google showed plenty of tutorials- I used http://blog.fosketts.net/2010/05/28/tune-apple-time-machine-frequently/

The article explains how to alter the desired /System/Library/LaunchDaemons/com.apple.backupd-auto.plist using Vi but I’m more familiar with nano:

  1. Open Terminal
  2. sudo nano /System/Library/LaunchDaemons/com.apple.backupd-auto.plist
  3. Locate <key>StartInterval</key> (you will see the value below 3600 (this is in seconds which equates to 1hour)
  4. Enter the new value in seconds- say 36000 for every 10hours
  5. Press Ctrl-X to exit
  6. When prompted to save changes press Y and enter