Ubuntu 12.04 installer not detecting extra hdd but the Ubuntu 9.04 installer CD does. My system (x86) has two hdd (1TB each, independent) 4G RAM. I run Ubuntu 11.04 on the one hdd (sdb). Had 10.10 running on the other (sda). Could always access either sda and sdb by selecting during boot up. Both systems were functioning without a problem. Formatted sda to change partitions and install Ubuntu 12.04. Using a USB stick as installer - not detecting sda (it does detect sdb). Successfully installed Ubuntu 9.04 on sda after giving up on ubuntu 12.04. Again both drives are working fine. But I still want Ubuntu 12.04 on sda. The installer still does not detect sda.
The problem seems to be rooted in the left-overs of a previous employment of RAID1. The problem was solved by installing the alternative installer ("Text-based installation") that can be found on the Ubuntu Releases page.
When asked to activate RAID configuration, select "No" and installer should detect the affected drive.