When I purchased my MacBook Pro Retina I maxxed out the memory, but I couldn't justify the premium for the larger Solid State Drive. I knew that going with the 512Gb SSD would require judicial use of storage and regularly cleaning out the stuff I was not using on the primary drive. Constantly using an external drive when I am at the desk is a lifesaver. I only pull over the stuff I need when I am working on a project and need to be totally mobile.
Today while I was doing some SSD housekeeping I noticed that for some reason I had 60Gb of "Backups" listed in "About this Mac" table. This surprised me since I have Time Machine set to backup to my external 4TB Seagate GoFlex drive.
After a little digging I discovered that Time Machine is smarter than I gave it credit for. Since I have it set to backup to an external drive, it occasionally attempts to run a backup while I have the MacBook undocked. Instead of just aborting the backup, it runs the backup to a hidden file on the internal drive. This is great if you are just worried about recovering an accidentally deleted file. However it does absolutely nothing for you if your drive fails or your MacBook is stolen. The latter two situations are what I want backups to protect against. In most instances the "Trash" folder adds all the security I need for accidental deletion. It just isn't worth it to me to loose 50-60Gb of precious storage for an added "idiot" filter.
So how do we fix it?
The solution is extremely simple. Just open Terminal and at the command prompt type:
sudo tmutil disablelocal
This will prevent Time Machine from running a local backup. If for whatever reason you wish to restore this function, just enter the following command into Terminal:
sudo tmutil enablelocal
This will allow Time Machine to again store its backup locally when your external drive is disconnected.
I really wish this was a simple switch in the Time Machine preferences. It seems kind of sneaky to allow Time Machine to gobble up precious storage when for many of us it's not really necessary. I can see how a careless user could find this useful, but for the rest of us we just need to keep in mind that when we are enjoying the freedom of working un-docked and off our local network that we have one less safety to accidental idiocy.
Thanks to the 0x4e71 Blog for the tip!
