My SSD is filled, my OS thinks it is 400 Gb?

Hi,

1- Have you used Time Machine locally on this disk in the past? (I mean: including the successive restoration of your system during system updates, that may have put them back to your disk) (please tell us since when, this may help others), and 2- Do you (really) need to keep these old backups?

If you don't need to keep these old backups, try:

Open Applications -> Utilities -> Terminal, and copy/paste (no sudo):

tmutil thinLocalSnapshots / 10000000000 4

(type return)

(wait for the cursor to come back in position) (it could take quite a bit of time...)

If you are on a APFS file system (I assume: already High Sierra) you'll see then a list of "normal" snapshots (from the last 24 hours). All the most ancient snapshots will have been cleared precisely to let some place for these ones.

The syntax is aimed to tell in command line to the Time Machine utility to thin local snapshots <mount_point> [purgeamount] [urgency]

That [purgeamount] is how much space you want to recover in the process, and the [urgency] is a number (1-4) of how quickly you want the space recovered. Both are optional.

Regards.

(Sorry, I wasn’t sure this was posted. So I copy-pasted the content from another app and got the weird formatting.)

FINAL SOLUTION & UPDATE:

Hello everyone, I appreciate all of your comments and suggestions. The final solution was resolved by a couple of Apple Genius’ at the Apple Store and required ERASING my SSD, something which I actually wanted to do after a certain point. Below I will bullet point some of the process — from my memory, so I hope there are no errors. Regardless, the final solution was rather simple—I’ll put that as the first bullet.

The information is anecdotal and not meant to be tech support.

• SOLUTION: To erase my “stuck” SSD in my iMac, the Apple Genius first ran a hardware diagnostics program that checked out that the disk was Ok. Then, using Disk Utility, he clicked on SHOW ALL DEVICES. This brings up the actual “device name” of the SSD drive, not just the named drive. Then the Genius, selected the device name and said Erase drive, selecting the traditional formatting (name of drive, OS X Journaled, GUID partition). The drive then FULLY ERASED freeing up the “hidden volumes” that had kept me from using the drive. Then the Genius reinstalled High Sierra which automatically reformatted the SSD drive as AFPS (or whatever its called). After which, I began to set up the computer, reinstall apps, reconnect to all my services and so on. I AM SO HAPPY. See the following bullets.

• WHY I COULD NOT ERASE THE SSD DRIVE: The Genius said that when High Sierra formats or erases a drive or installs itself, it adds a “new layer” of structure to the drive (I’ll call it Volumes) and thus trying to erase the drive using either the volumes or named drive does not fully erase all of the drive’s Partitions. Thas, you need to select the Device Name of the internal drive in order to erase the drive in it’s traditional sense.

• UNDERSTAND—FULLY ERASING THE DRIVE: The above is erasing the drive fully. To my understanding, there is no way to “delete” the “hidden volumes” of the drive to free up drive space, thus I was happy to erase the drive, free up ALL of the space, and start fresh.

• WHY I WAS “STUCK”: Besides being an idiot for letting my drive fill up and then causing additional errors due to syncing of iCloud and Dropbox—likely why everything became corrupted or confused—the computer could not “respond” to unmounting the SSD drive, or repair or erase the drive. It just was “stuck.” A prior Apple Genius suggested I try resetting the PRAM (Opt-Com-P-R keys on Restart). At first, it did not seem to work. A little later, the computer connected to Apple’s Internet Disk Utility. This is where I “erased” the SSD but it came back saying that I had only 6 Gb free and 490 Gb in hidden volumes. That is where I was stuck until the Apple Genius resolved the issue by properly reformatting the drive.

• BOOTABLE OS DRIVES? For reasons totally unknown to me, I could NOT for anything create any type of bootable OS drive (on external drive or USB key), following many instructions on the web.

• WHAT WERE THOSE HIDDEN VOLUMES? It is almost certain that the hidden volumes taking up 490 Gb were OLD Time Machine backups and many IOS backups to the computer. I had done both for many years. Apparently, these “volumes” were not freed up due to the High Sierra formatting mentioned above. And, we think, that there is no way to free these up without totally erasing the drive.

• TIME MACHINE backups? Yes, I had many. Then they failed (space issues). I did not use Time Machine to restore my content.

• DAISY DISK and CARBON COPY CLONER. I did use Daisy Disk which showed me the hidden volumes but even the standalone version could not access the hidden volumes. I was not going to randomly just delete large segments of the disks. Foolish. I did have a Carbon Copy CLONER backup of my drive, after deleting a bunch of stuff and did use the CCC backup on an external drive to run the computer — which did work under CCC. Not exactly sure how the CCC acted as a bootable thing. I did NOT restore from CCC because it would have brought back OS issues in all likelihood.

I‘m certain I forget some things but I hope this may help others in understanding at least why I could not erase my internal SSD drive and free up all of the space. I apologize for my long wordiness. :-)

My recommendation is to seek Apple Store Genius help when possible.

Thank you, everyone.

From terminal you can get a look at file size/ unaccounted for GB. Let it run its course:

sudo du -h -d 1 ~/

will list the items in the home folder with the sizes, including invisible items.

sudo du -h -d 1 /

will list the items in root with the sizes, including invisible items.

Hello jmaryn,

Please stop running terminal commands. That is likely to cause very serious problems.

The value reported for "System" in About This Mac > Storage > Manage Storage is just wrong. It is a well-known bug in the operating system.

If you want to know how much free space you have on your hard drive, open a new Finder window. In the View menu, choose "Show Status Bar" if it isn't already shown. The status bar at the bottom of the Finder window will show how much free space you have on your disk.

Hi,

We can try the same command with sudo and see if some backups are locked for some reason (and consequently have been left untouched).

sudo tmutil thinLocalSnapshots / 10000000000 4

(type return)

(enter your admin password)

(type return)

If it works, you should see the result immediately on your disk space, but better to restart just afterward.

Regards.