You can combine your disks in software as mirrored, striped, raid3,
raid5 or simply concatenated disks. Look for information on either
gvinum or the geom tools called gstripe, gmirror, and graid3. Unless
you really need these now, you might want to wait until you are
comfortable with creating Freebsd slices and partition. See the
relevant sections of the handbook, in which gvinum goes by its old
name, vinum. See also the ports/packages section of the FreeBSD
handbook for installing Apache/MySQL/PHP.