11.04 Grub2 no disks found HP Compaq dc5850 AHCI RAID

[cthart]

Hi,

The harddisk in my work PC died last week so I have replaced it with 2 new ones and am attempting to do a RAID1 mirror configuration and installation of Ubuntu 11.04 desktop.

Now the PC I use is an HP Compaq dc5850 which has fakeRAID so I configured this in the BIOS and attempted the install.

The normal Ubuntu install CD fails because it tries to install the bootloader to /dev/sda whereas it should probably be going to /dev/dm-0 (or /dev/mapper/pdc_<something> which is a symlink to /dev/dm-0). So in this case I installed Grub by hand.

The alternate CD install doesn't have this problem and seems to install succesfully.

After rebooting I get the dreaded "grub rescue>" prompt and a "no disks found" message. The "ls" command just returns a few blank lines.


A software RAID install works fine (using "native IDE" mode in the BIOS instead of "AHCI RAID"). I followed the recommendation in the HOWTO for software RAID and tested my configuration by removing the cables to my first drive. After reboot the machine came up, great! But then I powered off, reconnected the first drive, started up again and there's no disk activity, just a purple-brown Ubuntu screen.


Oh: I got a warning that I was using the DARK BLUE and LIGHT BLUE connectors whereas I should be using the DARK BLUE and WHITE connectors.


SO: I recabled and reinstalled using fakeRAID. Still getting "grub rescue" and "no disks found".


At this point I've lost 2 days work and I think I'll reinstall a softwareRAID and, untested, start using the machine.


What am I doing wrong?

Thanks,

Colin

PS bootinfo attached... the /dev/sda stuff wories me. Is this a left over from my previous install?? I had it the first time too, probably from the installer's attempt to put the bootloader on /dev/sda instead of on the DM device.