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Russ G Author

Level 1

73 points

Permissions Quagmire

I am running Catalina 10.15.3 on a mid 2015 MacBook Pro. I am trying to use BlackMagic's Disk Speed Test app v3.2 to test the read and write speed of the internal SSD. I am logged into my user account on the MacBook and it is an Admin account. When I try to run Disk Speed Test I cannot select the internal SSD on the MacBook. I get an error saying it is a Read Only drive. I tried using the Get Info window to add my user account but get the error message in the attached screenshot that I don't have the necessary permission. I also tired changing the "admin" listing in the Get Info window to Read & Write but I get the same error.

What am I missing?

Thank you.

Posted on Feb 15, 2020 7:21 PM

Top-ranking reply

HWTech

Level 9

60,626 points

Posted on Feb 15, 2020 7:56 PM

Catalina has changed the volume layout on the drive and tries to make this invisible to users, however, some apps like Black Magic's Disk Speed Test may have issues. The real "Macintosh HD" volume now only contains the system files and is read-only. The read+write volume containing your home user folders is actually "Macintosh HD - Data". See if you can select the latter option in the app.

Apple article with details on the read-only file system:

https://support.apple.com/en-us/HT210650

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