I looked at some of the other Q&A here and didn't see a duplicate of this one (e.g., How can I figure out what's slowly eating my HD space? and other linked and related questions).
Finder reports that my 500 GB drive is using 499.248 GB.
OmniDiskSweeper reports a bit more than 358.64 GB once it seems to have settled to final values:
Users 287.2 GB Applications 26.2 Developer 16.4 Library 10.9 private 6.2 lost+found 4.1 MSI 3.6 System 3.5 usr 0.4977 Google Earth.app 0.0461 others, less than .1 Total 358.7438 GB
(I got this by running sudo open OmniDiskSweeper.app, which gave the same result as running it without the sudo. It is reporting on hidden files.)
I also ran GrandPerspective on the ~Users folder, and it accounted for only 266 GB, which is 21.1 GB short of what OmniDiskSweeper reports. (By the way, GrandPerspective version 1.5.1 doesn't seem to be able to scan the whole disk, only folders. I htought I used it to scan the whole disk in the past.)
So, by OmniDiskSweeper's account, I have about 140 GB unaccounted for. Are there any other tools that might tell me where the rest is, or why it is tagged as used?
I ran Disk Utility Verify and the results reported are
Verifying volume “MacbookPro3” Checking file system Performing live verification. Checking Journaled HFS Plus volume. Checking extents overflow file. Checking catalog file. Checking multi-linked files. Checking catalog hierarchy. Checking extended attributes file. Checking volume bitmap. Checking volume information. The volume MacbookPro3 appears to be OK.
I don't do this often, but I think I would have expected a report of something wrong, which I would then fix by running Repair. It looks like there is nothing to do here.
df -h output:
Filesystem Size Used Avail Capacity Mounted on /dev/disk0s2 465Gi 464Gi 490Mi 100% / devfs 185Ki 185Ki 0Bi 100% /dev map -hosts 0Bi 0Bi 0Bi 100% /net map auto_home 0Bi 0Bi 0Bi 100% /home
Filesystem 512-blocks Used Available Capacity Mounted on /dev/disk0s2 975093952 973576656 1005296 100% / devfs 370 370 0 100% /dev map -hosts 0 0 0 100% /net map auto_home 0 0 0 100% /home
I looked in /Volumes for MobileBackups. There is no folder (or volume) there by that name. But there is a folder with my disk volume name, "MacbookPro3". I tried to get it's size with Finder. Information says it's an alias, so I imagine it's a link. When I look at information for what is in it, some of the big items (Applications, Developer, Library, MSI, System, and Users) add up to about 113 GB of usage, but is that real? If it is, then this might be the problem but I'm guessing I'm looking at linked folders.
Storage under About This Mac shows all disk space, 498.73 GB, allocated to "other". Everything else is literally "Zero KB".
UPDATE 3 I restore from Time Machine to a 750 GB drive using the most current backup. Looking at utilization on the new drive showed that it was consistent with the OmniDiskSweeper report above.
I then tried restoring to a virgin 500 GB drive and received the message that there was not enough room on the 500 GB drive.
I backed up the 750 GB drive to Time Machine, then successfully restored that backup to the 500 GB drive. The utilization on the 500 GB drive is consistent with the OmniDiskSweeper report above.
So both Time Machine and the laptop OS were confused about what the actual utilization was, overstating it by 120 to 135 GB. But Time machine was able to restore without including the lost disk space. But somehow Time Machine had the lost disk space in its backup records as space used, so when it tested a new drive for adequate space, it got it wrong.
I'm not sure what happened, but it looks like I was able to get it cleared up in a very round-about way. I have reclaimed over 120 - 135 GB of drive space.