For easier reference I'm copying the complete instructions below:-----------------3.1.3 Installing RHEL5 (with or without Update 1, Update 2, Update 3, Update 4, Update 5) on RAID-----------------In order to support XEN mode, the system needs to have its Virtualization feature enabled in BIOS as a first step, and XEN software package in the OS needs to be loaded during installation.1) Create a RAID array using the Intel(R) Embedded Server RAID Technology II RAID BIOS Console.2) Connect USB floppy drive and insert the floppy disk with RAID driver3) Boot your system using RHEL5.0 DVD4) At boot prompt type "linux dd noprobe=ata1 noprobe=ata2 noprobe=ata3 noprobe=ata4"5) And then you'll see a page that shows "loading usb-storage driver", and then it will ask you "Do you have a driver disk". Choose "Yes"6) Then it will ask you which one do you choose as a driver disk, choose "sda" which is the USB floppy disk. And then click OK to continue, you'll see the message "Reading driver disk", after it finishes, it will ask "Do you wish to load any more driver disks?" choose No if you do not have any more driver to load.7) (If XEN mode feature is needed, the OS installatng KEY is necessary and then XEN software package needs to be loaded) Then continue with the RHEL automatic installation, you can see that in the page where we select drives to use for installation, you can only see 1 disk (Intel MegaSR), this means the raid is recognized.8) At the last step of the installation (after all the packages are installed) RHEL5 prompts you to reboot. Do not click reboot button. Press Ctr+Alt+F2 to go to the text console prompt.9) type "cat /proc/partitions" you will see some info about the partition. For example, you might find several rows, one row might include sdb. You might find like thismajor minor #blocks name8 16 1440 sdb(In case cannot find 1440 under #blocks column, may need to remove and reinsert the USB floppy drive, then to run "cat /proc/partitions" again.)10) type "mknod /dev/sdb b 8 16" (8 and 16 are copied from the major and minor numbers in step #9, so that the numbers could change according to what is seen in step #9)11) type "mkdir /temp"12) type "mount /dev/sdb /temp"13) type "ls /temp" and you can find all the driver files are now in /temp14) Use cd command to enter /temp directory15) type "./replace_ahci.sh" to execute the script. It will remove ahci from /etc/modprobe.conf and blacklist ahci in /etc/modprobe.d/blacklist (replace_ahci.sh is also an example, and please implement the script even if the *.sh is with other name).16) Go back to graphic screen and reboot the system in order to finish the installation.
Are you saying that you got error running the command in step #12? If yes, what's the complete error message? What's the output of step #9?
I have the problem on rhel6.2. My hardware has Intel C600 Series Chipset SAS/SATA/AHCI RAID Controller. I set
- AHCI Capable SATA Controller to "AHCI"
- SAS/SATA Capable Controller to "Intel ESRT2 (LSI*)" on BIOS and cofigured software raid by Intel Embedded Server RAID Technology II Version SCU.11.010609301.
I use raid drivers   and version 15.00.0329.2012-1-rhel62-ga-x86_64.img for it but rhel says "No suitable device" for each driver.
Which driver fixes my problem?
The driver  is the latest. You may need to extract the image to a USB floppy drive. Also while booting from DVD press esc key to give 3rd party driver using the following commands:
Linux dd blacklist=isci nodmraid
For more details see the megasr_DUD_readme.txt file in the driver package.