[CentOS] install on dell precision 380 with RAID

All,

I am installing centos 4.1 on dell precision 380 with RAID on the 
motherboard.
I have setup the disks as RAID and when I get to the manual partition page
I see both disks???

It uses the intel matrix storage manager.

I was expecting to only see one drive?

Have I done something wrong?

Thanks,

Jerry