Hi, I have recently got an old 500Gb firewire HDD to mess around with. What I want to use it for is setting up various partitions on it so that I can have Sierra, el Cap, whatever installed on each of their own partitions, and boot whichever OS X/macOS I need off the firewire drive. (Yes, this needs a mac with a firewire800 port) Using Disk Utility, I can Erase the HDD and have one partition created, but the Partition button (or Partition from the right-click menu) is greyed out when I select the drive. Am I missing something here, or is it a 'feature' of OS X/macOS that it won't create multiple partitions on an external Firewire drive? (The partition option is available if I select the internal HDD/SSD). Any help or contribution gratefully accepted! Thanks! Edit: I've tried with Firewire800 or USB connections to the external HDD, still can't Partition the external drive.