For Lightroom catalogs (which include the .lrcat catalog file and the .lrpreviews preview files), the game changer in the performance area has arrived: the OWC Mercury Accelsior PCIe SSD, for the Mac Pro (only).
Putting the LR catalog folders on the Accelsior PCIe SSD means that all performance issues related to reading or writing all but vaporize.
In the Lightroom context, there is no reason that original image files cannot also reside on the Accelsior PCIe SSD, but there won’t be much benefit to doing so, and since such files are very large, capacity is better handled with a drive like the 4TB Hitachi 7K4000, perhaps a mirrored pair for fault tolerance.
Not everyone needs this kind of speed, and many tasks do not involve disk I/O (thus no drive can help), but for a seamless ultra-responsive drive that will let Lightroom work at full speed when the drive is involved, the Accelsior is it. Be sure to consider capacity needs for the catalog(s) including the previews.
Aside from stellar performance, the genius of the Accelsior PCIe SSD is that it leaves all the drive bays of the Mac Pro free for use. I have been using the 240GB Accelsior for some weeks now, to my great satisfaction, and that is coming from a triple RAID-0 stripe of 6G SSDs just prior!
I’m not a Lightroom user due to my workflow needs, but the graph below is instructive in just how effective the Accelsior PCIe SSD is in reducing disk I/O overhead with Photoshop CS6.
I am spec'ing all my MPG Pro Workstation builds now with the Accelsior.