How to install freebsd 8 on raid disk

[Sam Wun]

Hi,

I just bought a raid server,
Here is the current configuration:
"SC318 1ru Supermicro Rackmount server,
Intel 3G HT P4 Cpu, 1gig ddr400 ram,
4x 250Gig Sata2 Hdd in hotswap pull out caddies,
Adaptec 2420sa 128mb sata2 Raid card with latest firmware,
Dual 1 Gig Network ports
Hard Drive's are configurated as 1 hardware Raid5 volume
"
Operating system is FreeBSD 6,4m with FreeNAS installed / configured.

I want to replace it with FreeBSD 8.0.
When system boot up, freebsd 8 detected raid 0 and raid 1.

But when I installed, it said /dev/accdsxxxxx (can't remember the
name) not found.

Then I booted into the current system 6.4 have a looked its dmesg
message, and the shown the following configuration:

aacdu0: <RAID 0/1> on aacu0
aacdu0: 100MB (204800 sectors)
aacdu1: <RAID 5> on aacu0
aacdu1: 714638MB

I am wondering how to install a FreeBSD system on this server.

Very appreciate for any suggestion and pointers.

Thanks
Sam