Raid Chunk Sizes for DSS type DB

It's not an optimal setup but since I only have 3x500G drives to play
with, I can't build a Raid10, so I'm going for Raid5 to test out
capability before I decide on Raid5 vs Raid1 tradeoff. (Raid1 = No Fault
tolerance since 3 drives)

Anyway.. I'm trying to figure out the chunk size for the raid. I'm using
4k chunks since I'm reading that for DSS type queries, lots of Large
Reads, I should be using small chunks. [1] and I've aligned the disks
per [2]

and my stride will 3 for ext3

mdadm --create --verbose /dev/md1 --level=5 --raid-devices=3 --chunk=4 /dev/sdd1 /dev/sde1 /dev/sdf1
mkfs.ext3 -E stride=3 -O dir_index /dev/md1
mount /dev/md1 /pgsql/ -o noatime,data=writeback

[1] http://wiki.centos.org/HowTos/Disk_Optimization
[2] http://www.pythian.com/blogs/411/aligning-asm-disks-on-linux

Just wondering if there's any suggestions/comments on this from the PG ppl here.

Thanks for any/all comments.