Hi,
Just another quick update.
To make the installer work you have to disable the RAID or zero out the metadata (either at the start or end of the disk) so no raid is started. The disks should then appear in the installer. The installer needs to see a plain /dev/sda, /dev/sdb, ... instead of /dev/cciss/c0d0 and similar.
We can try this during the next few days and provide an update. As far as I understand, the disk controller (HP P420i) is RAID only, but perhaps it is OK to simply create a single-disk RAID-0 array and see whether the installer sees that. The interesting thing is that currently the RAID-1 array appears in the installer shell as /dev/sda. I read a bit about more advanced steps to turn off RAID on the controller, but it seems quite involved and not really something we want to try unless absolutely needed (e.g., https://systemausfall.org/wikis/howto/Disable%20HP%20Proliant%20Hardware-...).
Deleting the RAID-1 array for the operating system disks and setting the disks up as single-disk RAID-0 arrays did not help. The installer still fails to find usable disks even though the RAID-1 or RAID-0 disks appear as /dev/sda. Not sure where to go from here...
Best, Dave