I asked this over on the iMac section as well but figured I may have luck in this section: I am planning on getting the new 21.5" iMac but am stumped about this Fusion Drive. I see the benefits of being able to load Lightroom and Photoshop faster, but my question is this: If I store all of my image files on a standard USB external drive, am I losing the benefits of the fusion drive? I understand I would be better to have my images on an external SSD or Thunderbolt but that's not an option for me at this time (I shoot weddings and would fill up an external SSD in no time). Is my USB external drive going to be a huge bottleneck when editing images, transferring files etc? Thanks!