How to install Ubuntu Server on HP ProLiant MicroServer Gen8?
Solution 1:
You need to run the onboard Raid controller in ACHI mode (BIOS setting), as there are no released RAID drivers for 14.04 (just some in development ones that are not frequently updated). Downside of this, is if you need Raid, you will have to install a separate controller card or use software Raid.
For more details , see my answer: https://askubuntu.com/a/498137/48474
Solution 2:
The problem is that HP haven't got their RAID driver included into the distribution.
You have 2 choices: either set your BIOS to SATA AHCI compatible mode, or download the driver from and follow the instructions here:
http://h20564.www2.hp.com/hpsc/doc/public/display?docId=emr_na-c03742583