I have been re-configuring my home system to try and optimise the performance of the RAID volumes. I have just finished setting up a 6 disk RAID6 with a 64k stripe size (based on these benchmarks http://louwrentius.com/linux-raid-level-and-chunk-size-the-benchmarks.h…) and an external write-intent bitmap on an ext2 filesystem (to avoid any journal overheads).