Not recognizing raid controller Adaptec AIC7901

[enid vx]

Hi all,

I'm having some problems installing FreeBSD on my Supermicro server equipped
with :

Single channel Adaptec® AIC-7901 controller for Ultra320 SCSI
Host RAID 0, 1, 10 support

I have 4 disks which are configured in 2 Raid1,

the problem is when I try to install FreeBSd from the installer cd, it shows
only the separated disks.

I've added also ahd_load="YES" into /boot/loader.conf on the installation
cd,
also on the boot prompt
load ahd
load ahd.ko
and then boot

but again with no success .
It were recognized only the 4 disks as separated.

How can I make it recognize the raid ?

Thanks in advance.