I have an existing Ubuntu 10.04 desktop system setup and running on a hard drive (Drive A).

I'd like to add 2 more hard drives (Drives B & C, same size) to the system and mount them as a RAID 1 array.

How do I do that?

I know how to create RAID arrays during the installation, but I don't want to reinstall my system, and I shouldn't have to since my system files will stay on their own drive separate from the RAID array.

I've physically added both drives to the system, and formatted them as EXT3 with gparted.

Ubuntu's disk utility has a "create raid" option, but it won't let me select any of my drives (it thinks they're all full).

I don't mind using mdadm, but I've found several guides that are old, and give conflicting advice. Some say I have to edit an /etc/raidtab file, some say this is done automatically.

So what's the current (Ubuntu 10.04) preferred way of adding a RAID 1 to an existing system?

It should turn into a raid at boot, and mount itself in /home/myname/files/.

Thanks!