Hello Serverfault community. I hope someone can shed light on a peculiar problem I am having with an Ubuntu 9.10 server install. I am not a Linux expert but have the responsibility of fixing the box if something goes wrong. DOH! I have Ubuntu 9.10 server installed on on a desktop platform: Compaq Presario SR5027CL. There are two 1TB SATA drives configured in a RAID 1 array; I use the box as an email backup server for a small group of users. Last week one of the drives failed and was replaced with a new drive of the same type. The problem I have been having is getting the box to reboot after a restart or a shutdown halt. The OS and the RAID 1 array are on the same drives that make up the RAID 1 array. The replacement drive (sda) was added to the box and the partitions were created to match the existing good drive (sdb). The array is made up of sda1 and sdb1. I found an interesting point while checking the BIOS settings: there is a "HDD Boot Group Priority" section, and the new drive was selected as the "1. 3rd master"; the server wouldn't boot configured like that, but when I set the old drive to be "1. 4th master", the box will reboot. I'm checking some more things, but I would certainly appreciate any useful information. Thanks in advance.