The Ubuntu Live CD installer doesn't support software RAID, and the server and alternate CDs only allow you to do RAID levels 0, 1, and 5. Raid 10 is the fastest RAID level that also has good redundancy too. So I was disappointed that Ubuntu didn't have it as a option for my new file server. I didn't want shell out lots of money for a RAID controller, especially since benchmarks show little performance benefit using a Hardware controller configured for RAID 10 in a file server.
I recently migrated my network storage server, running Ubuntu Linux incidently, to a software RAID 5 configuration. RAID level 5 requires atleast 3 harddrives; giving you in total N-1 storage, where N is the number of disks in the array.
Disk failure, on the hardware side, is too broad to cover in any great detail here, but the following basic steps should be followed (of course, as noted, your setup may require otherwise). The scenario here is that one of your disks has just gone "bad." It's beyond recovery.
The evolution of computing is characterized by a vertiginous acceleration of speed and capacity. As we install sophisticated applications and make use of computers in more creative ways, storage needs are pushed even further. You can improve your disk performance by using a RAID-enabled desktop system running common OSS applications.