System Formatter Failed While Erasing External Hard Drive Mac

Solution 1:

The solution that works on both OS 10.11 El Capitan and on OS 10.10 Yosemite is:

  1. Open up Disk Utility
  2. Select the actual drive, which is the lower part that will most likely be greyed out:
  3. Then go to Erase
  4. Select MAC OS EXTENDED (Journaled, Encrypted) It's important to select Encrypted
  5. Then enter a password and wait.(It will run without a problem )
  6. Then you can again erase and take the password down and use your drive again.