help with raid 5 chunk size and filesystem decision

Hi,

I'll need to copy a 2 disk raid-1 into a 6 disk raid-5, most of my files are
small files (there's now around 2,000,000 files, ~50% < 16KB, ~80% < 200KB,
~95% < 400KB). My php script will need to unserialize (read) many small
serialized objects (files) (most of them < 32KB) from disk. My target is,
best PHP performance.

Will 32KB chunk size give me the best performance? Also for my case, will
reiserfs out-perform ext3 a lot? Does reiserfs have any problem with kernel
2.6 raid5? Should I use the unpopular raid4 instead of raid5 for best read
performance?

Wish that someone here can help me

Regards,
Kyle