Think I know what the problem is for some people

When this app is first launched you may have to seelct a folder for the test files on the disk you want to test. For my boot volume, I had to create a new folder and then use finder’s get-info to turn on R/W permissions for all on the test folder. Then it was fine.

The app and its GUI could be better. I’d suggest that the app show the list of drives/volumes you could test, it could flag if they lack space for test files or need permissions opened. When it runs it should clearly show A. That it’s running (all it does is gray out the gear icon and occasionally it updates the speed measured values), B. Which drive/volume it’s working on. In fact, it could show a table of all drives tested and their values. It could offer a checkbox next to each for you to indicate which volumes to test. This could work for network “drives” as well.

It would be a nice added step if it showed the name/model reported for each drive in the table, show the published specs for the drive, and then let you see in the table further drives of same or greater capacity, their prices on Amazon and other sellers, and then links to buy. Purchases through the links would benefit the app publisher. The main point would be that this tool could be a real world system upgrade planning tool.

Mark in the bay area about Blackmagic Disk Speed Test, v3.0