Yes, you can work with the photos on one of the RAID drives, and have the backups on the other RAID drive.
You have to point Lightroom to use the RAID drive instead of the internal drive. Please follow the instructions at this document (scroll down to the section entitled "Part 2 -- Updating Folder Location"). Future imports should go directly to the RAID drive instead of your internal drive.
Thanks! I know how to re-direct Lr to use the RAID drives on the Network...my main concern was speed issues.
But if Lr can get the speed from the Network drives needed, this will work MUCH better for me to streamline the process.
But those of us here on the Internet can't possibly know what your network speed is.
The only way to find out is to try it, by following the instructions I linked to; and if it is too slow, undo what you did and point Lightroom back to the original files on your internal HD.