I know it doesn't help you now, but this is how I logically installed my drives.
I put the pairity on the bottom since it was the biggest and I knew I wouldn't be changing it out any time soon, which is sda
As I installed the other drives I stacked them on top, which of course became sdb-sdf
On screen
a
b
c
d
e
f
in the machine
f
e
d
c
b
a
I know its kinda backwards, but thats how things went in and unless I go nuts I'm not sure how I can screw that up. As well each drive I put its serial number on the back.
Since this photo I've removed the blue cable which was my acting cache drive since I've decided it was not needed, but the red one is still my pairity drive.