I just purchased an iMac Retina with a 512g SSD. I plan to use this machine with a bunch of VM's to run some of the windows apps, along with doing testing and learning of linux etc.. I decided that as the VM's can take up quite a bit of space, and rather than fill up the SSD with stuff that really is not speed critical, I would put all the VM's onto an External harddrive. I have 4 1.0TB WD green drives left over from past installs that are perfect for this task. Right now I have a Vantac NexStar USB3 dual port doc that I borrowed from my NAS downstairs to try it out to see if external drives would be practical and fast enough. It works great. So I need to figure out a more permanent solution. Being in Canada, many of the discount stores just aren't available to me, and after putting in over $3500 for the iMac, I am a bit tapped out for big dollar spending. What options are there for a good case to put the drives into? If I wanted to get some form of mirror, do I need to get a hardware solution or is there some relatively inexpensive software to mirror to external usb connected drives? Would a physical case be better than sticking with something like a drive dock? Any help or suggestions greatly appreciated.