My 8 drive RAID array is a little weird. Throughput is decent, but latency is kinda bad. This causes World of Warcraft for mac to not be able to keep up when capturing in-game video at high data rates (200+ MB/s), which of course is the only way to get large frame size *and* high frame rate :) It took me literally years to finally think of this solution, and after a lot of fine tuning, it works great! The basic idea is to capture video files to a ramdisk and continuously move them to my RAID array during capture. See the script comments for the gory details.
Here is an example use of this fancy fast capturing in action. These clips started off as 1920 x 1200 @ 100 fps, which is about 300 MB/s during capture. FCP X was used to re-time the clips and export for YouTube.