I have a LSI Mega Raid set up containing two 4TB WD Drives on my Asus WS Motherboard. I want to use it to capture and record videos in lossless quality, too. The stripe size has 64 kbyte. When copying files from my ssd to the raid I reach about 310MB/s. Large files are copied or moved extremely fast.
But the problem is, that programs like DXTory write with a data rate of 12MB/s only. Several Disk Speed tests give me weird low performance results, also. The worst thing is, that I can't capture videos from my Blackmagic Design intensity Pro Capture card, because the recording program does not reach enough speed.
I installed the latest drivers for the board, and LSI software. No changes.
You have two non-raid capable drives running in raid0. While many people dont run into issue using these green drives there are many who do. It looks like your one and no one can really diagnose further. What I suspect is happeneing is while the write buffer is filling one or both of the drive is either spinning down or going to sleep. Do you have write thru or write back cache set? You want thru.