After MAC OS 12 Monterey update the System Data Folder swelled to incredible sizes after deleting files.
I actually wanted to reply to an existing thread on this subject but was unable to as it had been closed.
I have been having a terrible problem with this recently on my new iMac 27 inch
I had noticed that space on my 500gb hard drive was reduced to 10% so acted by deleting large unnecessary documents this was not effective as space was not released at all.
My dealer suggested I bring it in or phone free Apple Support number firstly, which I did and explained that there was a rumour and a problem with Monterey doing this ….but……. they were worse than useless and suggested I just move my iPhotos library to an external hard drive as it was 89GB to release the space then I should delete the iPhotos file from my hard drive. I did comment to them that once deleted I might still have same problem and their response was “we will cross that bridge when we come to it! “
I was correct in my assumption as the space on my hard drive DID NOT increase but System Data got even bigger! I did not call them back!
The next day I got a new iOS Monterey security / Safari update come up so I ran it and very strangely my iPhotos library had appeared back on my dock which was a relief actually as I prefer it there but the size of iPhotos had reduced from 89GB to 22GB what is that all about?
Also my hard drive available space had increased but from only from 50GB to 100GB ?
But, I still had the same problem that when deleting files to release space it does not appear but system data gets even bigger.
Then I had a brainwave, I ejected my old existing Time Machine desktop hard drive and attached a new portable external hard drive and started anew with back ups. After this had completed backing up I checked my storage and it had magically recovered over 300GB of space from the measly 100GB!
I am not sure what is going on here not being very aufait with this sort of thing but it seems to have worked, well so far fingers crossed. Just wanted to share in case anyone else is still experiencing this very annoying problem.
iMac 27″, macOS 12.6