why I cant see the 6 hard disk while install Debian on my server?

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http://serverfault.com – I am installing Debian 6 on a server, a HP Proliant DL380 G4, it comes with 6 hard disk, originary it has windows server, and I could see the 3 hard disk only (the other three said the Admin, were used as RAID 1) , so, now I want to install Debian and curiously when I want to format the disks I cant see the 6, just 3... why is this? do I have to do something special for make it recognize them? Thanks (HowTos)