Your problem is the capacity of your RAID.
RAID 0 was built to increase the speed. And WTH? Do you really have SAS drives in a desktop system?
The FPS loss is not caused by your hard drive, it depends on the settings of your recording software and your GPU. The most programs allow 60 FPS, some good tools allow more.
A good but time-consuming method is to use the ingame record command (/record f.e.) to your RAID. If you use this command, the file will be way smaller than a video file, because only the positions etc will be recorded as -let's say- coordinates.
You can record your session later with a screen capture tool.
With this method you don't have to worry about FPS losses and the problems they cause while you are playing.