Unable to Test Internal iMac Fusion Drive with Blackmagic

macos tips
1

I was measuring the read/write speeds of my external drives and decided to check my iMac’s Fusion Drive as well.

However, when selecting the drive, I receive an error stating it cannot be tested because it is “Read Only”. There doesn’t seem to be an alternative location on the internal drive to choose.

I encountered the same issue on my 2012 Mac Mini. How to fix it?

2

Hello, if you are unable to test the Fusion drive using BlackMagic Disk Speed Test, here are my advice:

If the drive is the first used, please check its file system in Disk Utility. If it’s NTFS-formatted drive, you’d better use NTFS drivers for Mac, which can read and write the read-only drive on Mac. iBoysoft NTFS for Mac is a good choice. If not, you can:

  1. Check drive permission. To enable the Read & Write access for your drive.
  2. Run the test on a writable directory.
  3. Disable System Integrity Protection (SIP) temporarily.
3

If Blackmagic Disk Speed Test doesn’t work, try an alternative tool:

AmorphousDiskMark
AJA System Test
CrystalDiskMark (Mac version via Homebrew)

But you need to clean and uninstall BlackMagic completely, for a total removal for the app and leftovers, CleanMyApp is highly recommended to you.