Hard Drive Space Discrepancy

Most of the difference you're seeing is due to Time Machine's "Local Snapshots" feature. When Time Machine is turned on but the backup device isn't available, it backs up to the local volume. The space used for these local snapshots is counted as "in use" by Disk Utility and System Information, but not the Finder (see the Disk Space considerations section of this article). While the space for backup actually is in use, it'll be freed automatically when needed (i.e. when the volume gets above 80% full), so the Finder counts it as being available.

In your particular case, the space System Information lists as being used for "Backups", 98.36GB, is very close to the difference in free space listed by the Finder vs. the other two. The Finder's 206.43GB free - 98.36GB of backups = 108.07GB actually free; compare to System Info's listing of 108.44GB free and Disk Util's 108.31GB. I'm not sure what the rest of the difference is (maybe they looked at the disk at slightly different times? Or they may be counting volume structures a bit differently?), but it's very small.

Finder shows:

• easily, the truth for JHFS+ volume Macintosh HD
• optionally, the truth for mtmfs volume MobileBackups

Hint: with local snapshots enabled in Time Machine, in Finder you can go to /Volumes/MobileBackups then get info.

Results of a one-line command show that for some purposes, MobileBackups is treated as a distant file system:

qlmanage -m disks | grep MobileBackups && mount | grep MobileBackups

As Disk Utility is oriented to local file systems, we'll probably never see MobileBackups as a separate volume in that context. There are degrees of simplification in Disk Utility, even when debug options are chosen.

If you are saying you have 1GB of free memory then the problem is not what is grabbing that 1GB but the lack of memory in the first place.

This will get worse overtime because you are already hitting 0 bytes and operating system needs space to write out its files.

I strongly suggest you move essential files like photos a video media off to an external drive to free up some memory. These type of files being normally the largest and easiest to move. ( Do not delete any system files unless you know exactly what they are and removing them will not break you system)

Try and give yourself at least 10-15% free space as a minimum and keep at or above that.