Need help with RedHat Advanced Server and shared SCSI storage

I don't know if this is the correct mailing list, so if not - please advise
where should I send it to.

I've installed RHAS 2.1 on two nodes. Each node has an Adaptec 29160N SCSI
controller. (Is there a problem with this one ?)
I am using an external scsi drive, connected to both nodes with a "Y" scsi
cable.

Installation completed succesfully, and so is cluster configuration.

BUT

After node A is up, when I start node B, it "steals" the shared scsi drive,
and it is no longer available for node A.
I notice that, because when I try to run "fdisk /dev/sda", fdisk does not
respond.

If I start node A after node B, node A would "steal" the shared scsi from
node B...

Any help would be appreciated.
Thanks,
Nir