Gluster users - Jul 2010 - any recommendations for configuring a Dell R510 w/ H700 controller?

I have four new Dell R510 w/ H700 controllers and 12x500GB disks each.  
Any recommendations on how to configure them for a scratch pool?

Raid5? Raid6? Raid50? Raid60?  All disks in one virtual disk (including 
root and swap)?  Default (64KB) stripe size or something else?  Write 
through/back?

My thought was to use RAID(x) for reliability and use GlusterFS to 
distribute the load across the four machines.  It's not an HA 
application: shared scratch-space for a Linux compute cluster.

Jeff Anderson-Lee
UC Berkeley