First, that's a lot of storage! wow!
Second, software raid and LVM are different subjects. Are you using all of this for Linux ( Clark connect or Red Hat)? If I were using it all for linux, I would install alllllllllll that storage. You would have a /dev/hda (applications) /dev/hdb /dev/hdc (250GB) /dev/hdd /dev/hde (500GB). Did I get that right?
m - (help)
1. n - new
2. p - primary partition
3. 1 - /dev/hdx1
4. (default starting cylinder) size: +2500MB (or +5000MB)
5. t - set partition type
6. fd - RAID
7. w - write and exit
***Do the same thing for /dev/hdb /dev/hdc /dev/hddd /dev/hde
# mdadm -C /dev/md0 -l 5 -n3 -x1 /dev/hdb1 /dev/hdc1 /dev/hdd1 /dev/hde1
#mount /dev/md0 /mnt/raid
/dev/md0 /mnt/raid ext3 defaults 0 0
Let me know if that works, I've never done this in your situation before.
For LVM. Use commands lgcreate, vgcreate, and lvcreate. (that goes in more depth)