I'm setting up a new mail server with 8x ST373455SS 15K.5 drives and the new Adaptec 5805 RAID card.  What are some recommendations for stripe size when configuring my RAID setup?  Note: I was going through the users folders and noticed that about 75% of the mail is less than 64K in size. Would it be better to configure the stripe size at 32 or 64K, or should I use the default of 256K?  Other options are 16K, 128K, 512K, and 1MB.
 
Thanks!

Mail servers generally store the mail in a large database file that is usually read/written in pages that are smaller than 64K (I believe Exchange uses 8K pages).  For that case, smaller stripe sizes would be better, as it would allow a better write combining hit rate.
 
I would choose 64K.

When i set my array up i used 256k although im storing large avi files and other bigger files.
 
In your case id agree with SomeJoe, with smaller read/write operations youd be better with something smaller