After Red Hat Enterprise Linux Has Been Installed

Creating a RAID array after Red Hat Enterprise Linux has been installed is a bit more complex. As with the addition of any type of disk storage, the necessary hardware must first be installed and properly configured.
Partitioning is a bit different for RAID than it is for single disk drives. Instead of selecting a partition type of "Linux" (type 83) or "Linux swap" (type 82), all partitions that are to be part of a RAID array must be set to "Linux raid auto" (type fd).
Next, it is necessary to actually create the RAID array. This is done with the mdadm program (refer to man mdadm for more information).
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[bc]1
mdadm --detail --scan > /dev/mdadm.conf
The RAID array /dev/md0 is now ready to be formatted and mounted. The process at this point is no different than for formatting and mounting a single disk drive.