Full Disk error message on iMac with macOS Ventura

Hello, I got a full disk error message recently. I have noticed that the disk space available for me as a user is only 19 GB while the volume OS Data has a lot disk space where it will not be used by me as a suer!!!

I have tried to solve this issue in Disk Utility but I couldn't increase the size of OS Volume. Thank you in advance for your help. I have posted earlier for the same but I thought to make it clearer in the post.


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iMac 21.5″ 4K, macOS 11.7

Posted on Feb 19, 2024 10:42 AM

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Question marked as Top-ranking reply

Posted on Feb 19, 2024 1:40 PM

9 replies

Feb 19, 2024 2:24 PM in response to rami.k

Ok, thanks.


Let's go over that.


With the newer versions of macOS, their internal drives are formatted in APFS. One change is that what used to be called Partitions in HFS+, are now called: Containers. Both of these can have one or more volumes; however, only APFS offers dynamic volumes.


When macOS is installed it is actually placed amongst a number of volumes. The core of the operating system is in two volumes. By default they would be called macIntosh HD & macIntosh HD - Data. Somehow yours got renamed to "OS" and "OS Ventura - Data" respectively. These are seen in the result as disk2s9 (System) & disk2s8 (Data). The System volume is read-only and sealed. You cannot, and should not, try to modify it in any way. The latter is where your data is stored.


There are also a few "supporting" volumes that make up macOS.


They are:

  • disk2s2 (Preboot)
  • disk2s3 (Recovery) << This is your Mac's Recovery "partition".
  • disk2s4 (VM)


Ok, what stands out, although it is taking up very little storage space (1 MB) is disk2s7 (OS Ventura - Data). What it looks like either you, or someone else, was "playing around" with the Disk Utility and created a new APFS "data" volume. This typically happens macOS was reinstalled to the wrong APFS volume and Disk Utility was not in the "Show All Devices" view when doing so.


The one you want is mounted as: /System/Volumes/Data. That would be: disk2s8. The one you will want to delete is mounted as: /Volumes. That would be disk2s7


The second issue is that the volume you want, disk2s8 has a size quota imposed on it. Again this would happen via the Disk Utility. It does NOT happen automatically. Currently, as you can see, that quota is set to 50 GBs. That's why there is so little disk space available for your data.



Feb 19, 2024 1:27 PM in response to rami.k

Do you have a fusion drive?

Did you replace the rotational drive of a Fusion drive with an SSD?

What model year is your iMac?

I don't recall a Fusion drive with only a 50 GB SSD portion. In order to apply updates you need a minimum of 50 GB of free space which you obviously don't have on the system portion of the drive.


You would be best served by getting a 1 or 2 TB external SSD and cloning your current system to it with Carbon Copy Cloner . That would give you plenty of room and free up the system portion so you won't get the "Out of Space" warning.


In the meantime make sure you have a full and current backup of your data drive with Time Machine or equivalent.

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Full Disk error message on iMac with macOS Ventura

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