When installing Ubuntu server edition (12.04 LTS), adding a RAID MD device fails from installer GUI. A workaround for this is to abort the installation after formatting partitions for RAID use, adding MD device(s) using the command line (mdadm), then boot back into the installer to continue the setup. Only after the raid MD device(s) is/are added via the command line with the installer show that MD devices are present and allow them to be used.
When installing Ubuntu server edition (12.04 LTS), adding a RAID MD device fails from installer GUI. A workaround for this is to abort the installation after formatting partitions for RAID use, adding MD device(s) using the command line (mdadm), then boot back into the installer to continue the setup. Only after the raid MD device(s) is/are added via the command line with the installer show that MD devices are present and allow them to be used.