Problem with adaptec raid

[olysyuk]

I have created(in bios) raid10 with four 500G hard disks.
Windows installation sees this raid device, and shows it's size as 930G

When booting latest AMD64 live-cd with "dodmraid" i see raid with
livecd ~ # dmraid -s
*** Group superset .ddf1_disks
--> Active Subset
name : ddf1_RAID_10
size : 976494592
stride : 128
type : mirror
status : ok
subsets: 0
devs : 4
spares : 0

but the size of this dmraid is equal to the size fo 1 hard disk (500G)
livecd ~ # dmraid -r
/dev/sdd: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
/dev/sdc: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
/dev/sdb: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0
/dev/sda: ddf1, ".ddf1_disks", GROUP, ok, 976494592 sectors, data@ 0

raid type is "mirror", and my adaptec raid format is identified as ddf1, not as (asr).
Any ideas?
1) why array is identified as raid 1 with 4 disks (while it should be raid 10)
2) maybe I'm missing some dmraid or kernel params when booting.