How can I delete (or at least reduce) the System Data from iMac?

Hi Kerem.

Just to clarify, in the first image below, the macOS and Mac System Data is shown in the red box, this is the amount of space that is being taken by the operating system and the files that the OS uses for system support. If this is very much bigger than ~90GB combined then that space can be recovered by reinstalling the OS.

The yellow box shows the space consumed by your applications and data, this space is not recovered by reinstalling the OS.

From your description of the problem it could be that Hit Film Express is responsible for the loss of storage space but I have no knowledge of this application.

If you refer to the second image below you will see that there is a tab called Containers.

Containers are just memory blocks on the hard drive where applications can store temporary data and it is possible that Hit Film Express is using a container for storage, there are no containers on my system, as you can see, but perhaps you will find containers on your disk if you look on the Containers tab.

Finally, the Manage Storage utility only finds files larger than ~50Mb and some video editing software breaks up video files into individually named and numbered small files that are smaller than 50Mb, which means they are not found in this type of search.

More experienced Apple forum users often recommend running a scan on your computer by an application called EtreCheck and posting the results log back here in your reply, perhaps you might like to try that and see if anything unusual is found?

There are much better experienced users here that might see something in your EtreCheck report.

You can download EtreCheck here: https://etrecheck.com/welcome

HTH.

Will.

Hi Berlin_Kerem

Review this linked Apple document on how to optimise storage space on your Mac.

https://support.apple.com/en-gb/HT206996

A useful tip, when you first launch the "About This Mac" utility and click on the "Storage" tab the bar-graph display always shows a large amount of System Data consumed but does not break this down further into discrete contents where the OS and Apple System Data is fully separated from User Data and Applications until the utility finishes scanning the disk, if you have a large disk and a lot of stored data this can take a while.

After opening the Storage tab you should leave this alone for five minutes or so for the disk to be fully scanned, after that time you will see that the "System Data" is broken down into smaller blocks and you may have a better idea of which applications have stored the most data.

For an in-depth overview of which files are consuming the most space click the "Manage" button on the "Storage" tab and then click the "Review Files" button to the right of the "Reduce Clutter" icon.

In the new window that opens you can see exactly which files and applications are taking the most space.

If you have deleted lots of stored data but the bar-graph on the Storage Tab does not change to show that the data has been deleted then reboot the Mac, which should then reset the bar-graph.

In very rare circumstances the growth of System Data occurs in the reserved macOS partition, sometimes after a macOS upgrade, if this has occurred then it is necessary to boot the Mac into recovery mode and reinstall the macOS.

For a Monterey OS and a typical Mac the combined total of macOS and Apple System data that is shown at the bottom of the left side pane of the "Review Files" tab totals ~ 90GB, if your system shows several hundred GB is being used for the macOS and Apple System Data combined then that might indicate that a reinstall of the OS is necessary.

HTH.

Hi Kerem.

I looked on-line for the Hit Film Express user manual and there are two important option settings to check.

1. In Hit Film Express Options look at the Auto Save options where the path to the enclosing folder for 10 minute Autosaves while you are working on a project are made, look in that folder and check to see if there are any orphaned project files that are taking up space.
2. In Hit Film Express Options look at the Cache options where the path to the enclosing folders for your Media Cache and TimeLine Cache are shown, you can check the contents of those folders to see if there is a large volume of data stored, also, on the Cache option page there are Delete buttons to empty those caches, make sure that when the delete buttons are pressed that the folders containing the caches are really emptied.

I don't think there is anything else I can suggest further from the macOS side that will help you.

If you run the EtreCheck test and post the results in your reply then hopefully one of the other experts here will recognise why your hard drive is filling up with invisible files.

Will.

Hi Berlin_Kerem.

No, you won't lose your applications and data when you reinstall the OS, on the Mac system the OS and your personal data are kept completely separate so you can re-install the OS at any time without penalty.

If you need to carry out a hard drive wipe and reinstall the entire Mac disk system then that is a different situation and in that case you should create a Time Machine backup to an external disk first, which saves all your applications and data, and then after you restore your Mac to the initial factory condition you re-import your applications and data from your Time Machine backup and you have lost nothing.

If you are are working with a video editing application check that it does not save project files as well as the working file, in this case when you create and save a .mp3 file, export it and then delete the .mp3 file on your Mac you may find that the original project file remains in your video editing application, which might explain why the disk storage does not decrease after you deleted the .mp3.

As described in the last reply, if you look under the "Manage" option of the "Storage tab" in "About This Mac" then click the "Review Files" button next to the "Reduce Clutter" you will see a list of all the individual (large) files taking up space in Storage and where those files are located.

Hi Kerem.

Do you use Time Machine for backup?

If yes there may be up to 10 local large snapshots for Time Machine on your system, this can happen when a Mac is used for processing very large files such as in video editing as those video projects become part of the Time Machine snapshots that are stored in the System Data area on your Mac.

If you do use Time Machine reply back and I will explain how to remove some of those snapshots.

The basic EtreCheck application is free, only the full version requires payment and for our purposes the free version is sufficient.

When you run EtreCheck make sure to grant Full Disk Access when asked otherwise it will not be able to see the files in the Mac System area and that is where your storage space is being excessively used.

After EtreCheck makes it’s scan you will see a share/export button at the top of the report, click that button to create the report that you can post in your reply.

Will.

Hi kerem.

If you have never used Time Machine before then the backup size of over 200GB is about right, this is a complete machine backup, all your apps and data, including system files.

The backup size shown when you looked at Time Machine is how big the backup will be, if you went ahead and made a backup to an external disk, this is not how big the backup is on your machine right now as it does not yet exist!

If you have never used Time Machine, and it is not switched on by default with a new Mac, then you will not have any local snapshots on your machine, however, if you want to check it is very simple to do.

Go to Applications > Utilities > Terminal

In the Terminal window type at the prompt (or copy-paste): tmutil listlocalsnapshotdates and hit enter/return.

If Time Machine has stored local snapshots a list of the last ten snapshots are shown, only a maximum of ten are stored and each new snapshot deletes the oldest one in the list automatically.

Each snapshot is listed by date and time in the format year-month-date-time, e.g. 2022-01-06-112530.

To remove the oldest snapshot(s) and free up some space in the Mac System Area then in Terminal type (or copy-paste):

sudo tmutil deletelocalsnapshots xxxx-xx-xx-xxxxxx

Where xxxx-xx-xx-xxxxxx is replaced by the name of the snapshot you want to delete from the list

e.g, using the above example you would type sudo tmutil deletelocalsnapshots 2022-01-06-112530 then hit enter/return to delete that snapshot, this is a slow process and can take some time if the snapshot is very large.

After the snapshot is deleted check back in About This Mac > Storage > Manage > Reduce Clutter > Review Files to see how much space has been recovered from the System Data area.

Repeat the process to remove additional snapshots.

As mentioned above there should be no local snapshots on your machine if you have never used Time Machine.

If you are going to use your Mac mainly for video editing then consider using an additional external SSD hard drive, as the professionals do, and point your Hit Film Express application to store it's caches, projects files and raw video data on that external drive instead of the Mac's internal drive, that will save you cluttering up the internal SSD drive and help keep the Mac performing well.

For your question regarding other caches stored in the Mac System Data area, yes there are lots of Mac system files as well as some app caches stored there but it is beyond the scope of the user forum to describe these in depth as this is really developer territory. Deleting cache files without understanding what the impact may be could cause the OS to be damaged, and as you have no Time Machine backup to recover from you could loose access to all your personal data and purchased software.

I don't think there is anything else I can suggest, other than as mentioned before the EtreCheck report might show you where other unused files or problems exist on your system that might be resolvable.

Will.