Time Machine Folder size and quantity of "items" less than computers?

[jman995x]

Hello,

I just started using Time Machine and my understanding is that it backs up everything on your computer.
Well, before I started deleting things on my computer to make more room I thought I'd pull up random folders (Pictures, Music, etc.) on my computer and also the same backed up folders on the Time Machine external drive, then Cmd + i them side by side....but the Time Machine Folder sizes and number of "items" are coming up just a little short of the originals on the computer itself.
Am I missing something, literally and figuratively?

I don't know if this matters, but I did the backups because my 111GB MB had zero (that's right, zero) space left on it. So, I backed up to a 1TB external HDD.

If the back did in fact leave off some "items", how would I go about finding out what those are? I don't want to start deleting things off the computer drive until I get an answer to this question of why the Time Machine numbers are just under the computer's numbers.

Thanks,

jman995x

 

[J the Ninja]

Time Machine ignores a whole bunch of replaceable things, mostly caches. This probably accounts for most of what is missing. Also, are you looking at just the original backup? TM does not copy a file version it has copied before, it will simply hardlink to the original copy it backed up. If you are curious about the gritty of what TM is leaving off, sift through this file:

/Library/Preferences/com.apple.TimeMachine.plist