Dell CERC SATA 2S question

[Jonathan Reeder]

I just got a Dell PowerEdge SC420 (or something like that) with the CERC
SATA 2S RAID.  When the server boots, the Adaptec utility tells me that I
have one array configured, a RAID 1 with 2 drives.  However, when I launch
the 5.3 installer and go to Allocate Disk Space options, it sees two drives
rather than the single RAID array.  The two drives it sees are ad4 and ad6.
I get an error when I select either of them, saying:

"A geometry of 310019/16/63 for ad(4|6) is incorrect.  Using a more likely
geometry..."

Any thoughts on how I can get FreeBSD to see my SATA array as an array
rather than as two separate drives?

Thanks a bunch.

Jonathan Reeder