oddmake's Journal: RAID4

I was taught only practical RAID-tech is RAID 5,1,0(or combination of 1+0),and no RAID-2,3,4 is developped and available.
But recently I found Fujitsu has RAID-4 storage server(http://storage-system.fujitsu.com/jp/term/raid/07.html)

# I'm a kind of Fujuitsu guy.

Why RAID-4?
RAID-5 has all the advantages of RAID-4,plus its know-how and merits and flaws are all well-knownn(compared to rare RAID-4).
You may be able to consult with Google for any time for any trouble.(Correctness of answer is not guaranteed,but you can try)

Why RAID-4?
Does RAID-4 have any advantages over RAID-5?

Any Comments and Suggents(especially from RAID-guru) are welcomed