altering defaults

[prad]

i'm new to xfs (courtesy of most helpful and encouraging commentary by
stan hoeppner!) and i've seen some advice which says to make the 
block size     -> 512
directory size -> 4096

on the other hand, i've also come across webpages which say don't mess
around! keep the defaults as they are unless you are absolutely sure
that changing it suits your purpose and know why.

my question is for the data storage area on a web/email server. we're
mainly going to have small files there and the email part will have only
temporary files for the most part since people will download (ie pop).

it makes sense to make the block size = 512, but i wonder if it really
matters noticeably. the server is not a heavily visited one and only on
very rare occasions will we get around 50000 hits/day - most of the time
we're looking at under 10000 and that is with all the domains combined.

-- 
in friendship,
prad