OOh! Nice system! Looking at the X2270 Spec, it doesn't appear to have any hardware RAID controller so I'd assume that it must be done in software. As you're asking in this forum I'd guess that you're using some form of Linux rather than Solaris? I've never tried a software RAID set up yet but I've only got an old Ultra 2 dual booting Solaris 8 and Gentoo. Most of the Sun hardware RAID kit I've played with has been T3,SE3300 or SE3500 arrays so, er... I'm not being much help.
I think we'd need to know what distro you're running for starters, plus I've noticed quite a few people with RAID questions, they may have been put off looking at your post as Sun usually run Sparc processors rather than the Intel Xeon jobs you've got. I'd assume that you'd need to set up a software RAID in the same manner as anyone with an HP, Dell, Acer, etc, Intel Box. I'd scan the forums for more info on software RAID set up and give that a go
Hope this is helpful...