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User profile for user: boxrainnmac
boxrainnmac Author
User level: Level 1
4 points

“Invisible” volume on internal drive

Using Disk Utility I can see a unmounted volume called Data that’s taking up over half of the drive’s disk space, but I can’t figure out how to mount it to see what it contains. I didn’t create it (to my knowledge) and I don’t know why it’s there. I’m comfortable with Terminal if that’s what it takes to mount it/see its contents, but of course, it would be better to access with the MacOS interface. I also tried Startup Disk in Sys Prefs to see if Data volume was bootable, but it wasn’t an available option. Also, I couldn’t find a file/folder with invisibles turned on for /System/Volumes/Data. How can I see it and is it safe to get rid of it?


Posted on Nov 14, 2023 9:15 PM

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User profile for user: HWTech
HWTech
User level: Level 9
60,650 points

Nov 15, 2023 10:48 AM in response to boxrainnmac

FYI, the "Data" volume is mounted and is shown as such in your screenshot of Disk Utility. Mount point is "/System/Volumes/Data".


Here are two Apple articles with some information about the new drive layout used by macOS 10.15+ (very simplified explanation):

About the read-only system volume in macOS Catalina or later - Apple Support


Signed system volume security in iOS, iPadOS, and macOS - Apple Support


What is a signed system volume? - Apple Support


Like @etresoft mentions, the storage is very complex & confusing. macOS does a lot of things behind the scenes & hides much of it from the user. Sometimes even the command line will hide some things from the user.

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User profile for user: boxrainnmac
boxrainnmac Author
User level: Level 1
4 points

Nov 14, 2023 9:52 PM in response to Niel

Thanks, but it’s hard to reconcile. In Finder window Macintosh HD, I have 4 folders:

Applications, Library, System, and Users. I can look at Get Info for each of those 4 and the total usage on disk for all 4 (including System) is about 100 GB, about 77 GB excluding the System folder. When I check the invisible folders—bin, cores, opt, etc—they are mostly empty or use insignificant space. Per Disk Utility there’s ~494 GB total drive space, ~205 GB free, and ~288 GB used. Can there be 188 GB used disk space not accounted for by those 4 folders?

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User profile for user: etresoft
etresoft
User level: Level 9
51,038 points

Nov 15, 2023 4:15 AM in response to boxrainnmac

boxrainnmac wrote:

In Finder window Macintosh HD, I have 4 folders:

Finder is very misleading. What you see in Disk Utility is an accurate display of your used and free storage. You will see different values anywhere else you look. And it will never add up.


Furthermore, what you see in Disk Utility, although the total is correct, is an extremely simplified view of your file system. It is much, much more complicated than it appears in your screenshot.


Depending on literally dozens of different factors, you may have additional storage taken up by local snapshots, temporary files, and "purgeable" data. You still have 200 GB free, so you have no problems and nothing to worry about. The more you delve into this, the more problems you will have. If you decide to take action, you'll have big problems. Leave well enough alone.

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“Invisible” volume on internal drive

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