Just a quick update, to let you all knowing that the private datacenter is now redundant IaaS. The only thing it does not offer (yet) is a redundant network.
The main cluster filesystem is spread over 4 hosts on 2 locations, which should improve reliability. Its also reliable to assume, that when you mirror hardware completely, you no longer need a raid-X but only a striping raid, since the whole FS is backed up on multiple hardware hosts.