There may be a normal /boot partition rather than a raid partition for raid5.
Look at your /etc/fstab file. This contains the devices and mount points for the mount command at boot time.
Also look at the output of:
sudo /sbin/fdisk -l
This will print out all of the partitions on you system, even if they aren't mounted.
If this is a server that you ordered, it could be that the lion's share is mounted on /srv.