I am planning on purchasing a new Dell PowerEdge server with 3 hard drives. The operating system will be Linux and this server will be our mail server (100-150 users). I know RAID 1 or 5 levels are best for a fault-tolerance solution, but can the root file system and/or /usr file system be placed on RAID 5 disk? Do I need to mirror the root file system? What would be the best RAID configuration and can someone give me step by step instructions on how to do this?