Okay, so the improved Core Storage has now been in Mountain Lion for a while, and I have a few questions for anyone familiar with it, or that is able to experiment with it. Fusion Drive and Apple RAID Firstly, has anyone checked to see if an SSD and an Apple Raid can be combined into a Core Storage volume? I've managed to convert an Apple Raid to a single Core Storage volume before by following this guide, but I'd be interested to know if I could then add an SSD to create a Fusion drive, as in most cases reading/writing to the SSD will still be faster, but with a striped set for the main capacity of the volume it should still be possible to load very large files fairly quickly. Fusion Drive and Tiering We know by now that what Fusion Drive does is essentially tiering, whereby more commonly accessed files are moved to the SSD for speed while everything else goes onto the slower drive(s) for capacity. However, does anyone know if Core Storage supports more than two tiers? For example, if I had an SSD, a 15,000rpm drive and a 7200rpm drive, would Core Storage take advantage of the 15,000rpm drive's speed or does it simply treat all non-SSD disks as one big pool for dumping less frequently used stuff into? Does anyone know also how Core Storage decides to use tiering in the first place? Guides for creating a Fusion drive yourself seem to simply involve add an SSD to a volume, at which point you've got a Fusion drive. Is there any flexibility in the behaviour, or any way to tweak it? How does it treat USB disks? Expanding a Core Storage Pool How well does Core Storage support adding extra drives to a pool after it's been created? For example, my current main set of drives has around 3tb of space, but with my use of video files that's not going to last forever. How easy is it to just add an extra disk and expand the volume to include the new disk? e.g - if I bought an extra 1tb disk and either added it to a spare SATA port or plugged it in externally, then I can just throw that capacity onto an existing volume? My Proposed Setup What I'm hoping to do is something like the following: 120gb SSD drive for Fusion Drive aided speed 4x 750gb hard disk drives as a RAID-0 set for large file speed 1tb+ hard disk drive as extra storage 6tb of NAS for Time Machine Is such a setup possible, or will it fail miserably? Currently I have the SSD for OS and users and the RAID as a files volume for larger folders, managed using symbolic links, but the whole thing is a giant pain in the ass as while it doesn't break anything exactly, loads of applications don't follow symbolic links which leads to a bunch of annoyances. Plus when the SSD starts filling up finding stuff to move every so often isn't exactly my favourite task either I know that Apple RAID isn't the fastest, but it's mostly been for large files anyway which it's always been perfectly good for.