While your co-worker is correct that the Fibre Channel payload is
approximately 2k, the logical leap that you would want to match your
blocksize to the Fibre channel payload size is completely erroneous.

Having a blocksize of 2k as opposed to 256k induces a 128 fold increase in
the communication overhead.   I.E. for every 256KB of data you are going
through the protocol overhead 128 more times.

It's like buying groceries, but instead of filling up your cart and taking
it to the checkout cashier,  you get 1 item at a time and bring it to the
cashier.  But you not only bring 1 item at a time, but you pay for each item
individually.   The checkout cashier's bar code reader can only handle one
item at a time, so you might as well get one item at a time.

The tape drive and the fibre channel protocol both perform significantly
better at 256KB blocksizes.

James Thompson


_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com