Time Machine disk w/ more free space than source?

[Analog Kid]

How is it that my Time Machine disk has 30GB more in free space than the source drive?

Both source and TM are 2x500GB RAIDs, my source drive says 129GB avail, while TM says 157GB avail after more than a week of backups...

I don't have any exclusions set in Preferences, is it excluding something by itself?

 

[Theatrics]

Not positive, but isn't this because time machine doesn't back up system files?

 

[Analog Kid]

Not positive, but isn't this because time machine doesn't back up system files?

I haven't gone through and done a file-by-file comparison, but I have restored system files after screwing things up so I think at least most of them are there... 30GB of system files seems unlikely anyway.

My main concern is that I'm working with a false sense of security.

 

[priller]

I've just noticed the same, 15GB used on my MB disk & 12GB used on the Time Machine disk.

 

[anthonyjr]

It's very possible that Time Machine uses a special compression technique?

I'm about to purchase another hard drive today to setup Time Machine on my Mac Pro next week. I can report back to let you know how it goes.

 

[priller]

I've found the 3GB difference on mine, almost 1GB of cache files & over 2GB of swap/sleepimage files.

 

[HLdan]

I've just noticed the same, 15GB used on my MB disk & 12GB used on the Time Machine disk.

Since your TM disk is smaller could that mean that you have only specified certain things to be backed up or are you backing up everything on your drive.

 

[priller]

Nothing excluded, as above I've found where the size difference is.