I have a mid 2015 MacBook Pro that runs Catalina. I want to use BlackMagic to test the read/write speed of the internal SSD. To my surprise, I can’t select it. An error message tells me that it’s a read-only drive. How can I run the test?
Run iBoysoft DiskGeeker for Mac to test the speed of your internal SSD.
macOS Catalina deals with volume layout different than previous macOS. You need to select the data volume Macintosh HD - Data rather than Macintosh HD, as it’s a read-only volume containing system files.