From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Question of PCI bandwidth affect on SW RAID arrays. Date: Fri, 27 Oct 2006 17:43:08 -0400 Message-ID: <45427D6C.7030909@tmr.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Justin Piszcz Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Justin Piszcz wrote: >Quick question, > >On older systems, regular PCI motherboards, no PCI-e-- which is faster? > >1) One 4 port SATA150 card in 1 PCI slot which has 4 drives connected. >2) Four SATA150 cards in 4 PCI slots, which each have 1 drive connected? > >I'd assume 2 would stress the PCI bus more and thus would be slower, but I >am curious what other people know/think/etc? > You are sending the same amount of data over the bus in either case, assuming you are using s/w RAID. This is where (real) hardware RAID has an advantage in performance, the parity doesn't go over the bus. If you have a server board it may have multiple PCI busses, and therefore a higher max bandwidth with multiple cards. I would still expect PCI-e to be faster. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979