Trying to Test Read/Write Speed of Internal Drive but Can't Select it

General
1

I have a mid-2015 MacBook Pro runnign macOS Catalina 10.15.3. I want to check the read and write speed of the internal hard drive with BlackMagic. However, it doesn’t allow me to select the internal SSD on the MacBook. An error says it’s read only. I checked the drive with Get Info and tried to add my user account but it said that I don’t have the necessary permission. How to fix this?

2

Apple introduced separate system and data volumes in macOS starting with macOS Catalina (10.15) in 2019.

Unlike the traditional single Macintosh HD volume, the internal drive now has two distinct volumes. The read-only system volume Macintosh HD, which is the one you tried to select, contains core system files. The read/write data volume Macintosh HD - Data stores user files, apps, and settings.

You should select the data volume to test speed.

3

If BlackMagic doesn’t show you the data volume, try a different tool. Download iBoysoft DiskGeeker for Mac, select the data volume, then click Speed Test to test the read or write speed.