As to the first question, Simon, there may or may not be a command available on the system that allows for RAID creation. What thing are you using at this time? If you have a Linux Live CD or a drive which supports booting (like a USB diskette drive or USB CD drive), then you can try to plug that in when the computer is on, put the Linux CD or diskette in, reset the computer, and press F12 or what key have the documentation to support the boot device. Once in the menu, elect boot of the device which the diskette is in (for instance, the boot diskette which may cause the CD to boot may be labeled the floppy drive). This will hopefully cause the Linux system (on the media) to access the CD drive (unless the CDis the boot device, in which case the system will boot to install or command).
There are several ways to create a RAID device in RHEL4 Setup. Read the documentation or look at the things that appear to be able to set it up. I believe that the RHEL4 Setup allows you to create a RAID or LVM diskette. I believe that you have to select the diskettes after clicking the RAID button (since that is, I believe, the desired thing you want), but BE CERTAIN THAT YOU HAVE THOSE DISKETTES CONFIGURED, EITHER IN YOUR HEAD OR AT THAT TIME!!! Sometimes you have to define the partitions in the Setup before you commit the RAID creation execution. Once you have that all in place, tell the Setup that you want to use the three diskettes (this is why you must have them set up, because it may ask about which partitions, how many diskettes, et cetera). Follow the instructions or options, and then set the system up and install the Linux system. Also, it is SERIOUSLY advised that with the system (in particular, RedHat) you create a /boot partition (preferrably on the mnain hard drive, preferrably on the initial partition, preferrably of type vfat, because that way you can boot other systems or if you want, other kernels), set up a ~ or /root partition (NOT one of the RAID diskettes), and then set up the others.
The RAID diskettes may be any partitions (like one on the main, three elsewhere, or whatever you want), because Linux will create a RAID device (/dev/md0 or whatever; the 'md' is for metadisk or multidisk). When set up, the system will start, and you will have the RAID device start when it does.
Does the device have to be formatted? Yes, but the software will take care of that, because when you go to set up the software, RedHat (as well as other Linux things) will format all of that when it begins the setup.
If you happen to set this up WITHOUT setting up the RAID device during Setup, then IMMEDIATELY UPON SUCCESSFUL SETUP, execute the following commands in the terminal:
This way you can set it up with all of the man and info stuff organized, and you have the help on the system
I hope this helps; I have had experience with the RHEL4 and I have a System Administration book on RedHat Linux (which I recommend you purhase a bbook on it because not everything regarding help is contained in the system). Good luck with the Linuxc system, and I recommend only one usage of some of the diskettes: BACK UP ANYTHING AT ALL THAT MIGHT EVEN SCANTLY BE REGARDED POSSIBLY AS VITAL INFORMATION!!!