Okay so, with details of how Fusion drive actually works now trickling out I'm curious about how it works, as I may be finally getting around to upgrading my main machine to Mountain Lion (I've held off because I didn't have my second point of backup up and running). Anyway, my current setup is an SSD system disk, and four 750gb drives in a striped apple RAID set. Basically what I'm wondering is if anyone has tried any kind of similar setup with Fusion Drive to see what kind of mileage they get? And I assume it's bootable? Setting up a RAID volume with CoreStorage is a bit tricky (I followed this guide), but after that it should be easy enough to stick it in a logical volume with an SSD, at which point Fusion Drive should kick in automatically. I'm hoping to use it as a simpler solution to managing two separate volumes manually, as that's only proven to be a pain in spite of the relative advantages of each (the RAID having massive capacity but with strong read speeds on large files). If anyone's got some spare drives and would be willing to test whether this is possible with Fusion support then it'd be greatly appreciated. For all my heaps of drives I don't actually have enough spare to try it myself!