Low disc space on boot drive mystery

[justinhill]

My Mac Po 6,1 was purchased used and my first action was to clone my existing Macbook Pro onto it - so on day one the two machines were essentially identical.

Since then, I haven't installed much in the way of new apps - but I removed a lot of apps copied from the Macbook that weren't relevant to my Pro Tools machine e.g. Office, Adobe suite and so forth. Since then I've ignored the boot drive - until Clean My Mac pointed out to me that I was running out of space.

Both machines have Apple original 500GB SSDs, formatted APFS. The Macbook currently has 140GB free space, the Mac Pro now only has 38GB. Running Clean My Mac's Space Lens to look at the folders on both machnines I can't see anywhere this extra 110GB can be. All folders are around the same size or smaller, but the space used on the Mac Pro's drive is real - the backup reports the same size.

(All my audio, VIs, etc. etc. are on external SSDs.)

I wondered if somehow TRIM was something to do with it and so I issued a Trimforce enable command on the Mac Pro. This hasn't changed anything.

Other differences between the two machines are of course there's much more RAM on the Mac Pro, and there are a number of external drives attached. But I can't see how that would be relevant. Any thoughts? The machine is working fine but I'm worried I'll run out of space altogether soon.

[JFreak]

many kinds of dumps happening when your software/plugins freak out so unless you have explicitly disabled them they keep adding up as you use your computer. to me it just seems you use your trashcan more than your laptop, nothing more.

[justinhill]

I've explicitly emptied the trash and do so on a regular basis.

While I was writing my original post I did a screenshot of the drive's Get Info. Since then, the machine has been sitting idle with nothing running. Used space has gone up from 459.180GB to 459.405GB i.e. 225MB has disappeared...

[justinhill]

Space is still slowly draining away without my using the machine. Looking at the Finder view of the two machines (see attached), I know there's some stuff I can't see but on the macbook the "stuff I can't see" seems to add up to just under 40GB.

On the Mac Pro, the "stuff I can't see" adds up to nearly 196GB. What is this stuff? Logs? Something produced by Pro Tools? Can I delete it?

[Ben Jenssen]

Do you regularly restart your mac? That often releases some space that apps had used for temporary files, caches and such.

[Darryl Ramm]

Lots of places to look to see where stuff is growing.

Core files and logs are suspects. Look at all the logs shown by Console.app. /var/log, /usr/local/var etc.

Even simple old UNIX things like syslog have been made much more complex under the covers by Apple and it does not take much to go wrong to spew content to them.

It's also possible for badly written or malicious programs to consume space and not be essilly found (process has a file open that has been unlinked and does not appear in the file system but still consumes space).

You can start by using find to search for large files and seeing if they are growing. Lots of easy ways... e.g.

$ ls -lS *

... file listing sorted by size. (watch out for hidden files and directories)

$ sudo find / -type f -size +1G

...to find all files over 1GB

$ sudo find / -type f -size +1G -exec du -m {} \; | sort -r -n

... to sort files by over 1GB by size displayed in MB.

There are ways to continuously watch a file size, see all files that a process has open, find what processes have a file open etc. All just a google away.

[justinhill]

I tend to leave my machines on 24/7 and re-boot only occasionally. Actually, Ben, I did reboot a couple of times yesterday hoping to regain some space but no luck.

Darryl, thanks for your comments too. I will go looking for giant log files and so forth. I'll have to be quick - overnight another 1GB disappeared by itself...

[ChuckS]

APFS Snapshots?

[justinhill]

Chuck,

Good idea... having discovered the relevant commands I asked tmutil to thin my snapshots by 20GB and - gosh - 20GB of space appeared on the boot drive.

Whether this is the answer to my original problem remains to be seen, since space is still reducing by itself on the Mac Pro but not doing so on the Macbook Pro which is also using APFS. On the other hand, the Macbook Pro doesn't have a rigorous backup regime like the Mac Pro does. I use Carbon Copy Cloner and the snapshots are being created by CCC.

My old friend and mentor now passed away, Jon Hiseman, used to moan about how you couldn't make records any more without being a self-taught IT specialist.

[ChuckS]

CCC creates it's own snapshots that need to be handled by CCC. In the app the drives are listed in the lower left hand panel. Click on a drive and it will show you the CCC snapshots in the right hand panel. You can delete them from there - I believe right-click on snapshot. Don't have it in front of me now