[CentOS] Dell mirror raid boot problems

Everyone,

I was recently given a Dell raid 386 server that had drives that had
gone bad.  I replaced the drives with a couple terrabyte sata Seagate
drives, and set up the bios for a mirrored raid configuration.

I was able to install Centos 5.2 without difficulty, but when it was
time to perform the 1st boot it went to grub instead of booting off of
one of the mirrored drives.

I could not figure out how to boot through grub, so I changed the bios
to look at both drives unmirrored.  At that point I was able to boot to
one of the drives, and the second drive was not mounted.

The raid logic is within the bios and mother board of the Dell machine.
Can any of you point me to some literature about making this system work
as a mirrored raid system.

Thanks,

-- 
Greg Ennis