Mirrored Drives Without a Controller?

We have a server that has SCSI drives at 18 GB. No RAID controller was purchased for the server and I’ve been researching whether you can mirror drives without the controller. Part of the one drive is FAT (utilities) and we would prefer to not have to reconfigure to make it NTFS but if that is the only way, then we will do it.

Is there any other way (since there is a SCSI controller) to mirror these drives? Thanks!