I have a similar problem with Dell PowerEdge servers. I have an IDE drive installed to use as root and 2 scsi drives being used as stand alone disks but running on MegaRaid controller card. While installing the drives show as sda, sdb, and sdc. The sda is the IDE drives. (i wish these were still named /dev/hd not /dev/sd). Install everything normal to sda. After reboot the system will fail to boot past grub. when at the initrmfs-tools screen I did `ls /dev | grep sd`. I found that I had a /dev/sda. /dev/sdb along with /dev/sdc1, sdc2, and sdc5. I rebooted and edited the grub menu to change the boot device from /dev/sda1 to /dev/sdc1. I was then able to boot into the system just fine. I manually changed this setting in grub.
