From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: Port Multipliers Date: Wed, 16 Sep 2009 16:34:50 +0100 Message-ID: <4AB1059A.4010705@anonymous.org.uk> References: <70ed7c3e0909100911q926fa9cs9185854b15dd8764@mail.gmail.com> <70ed7c3e0909101144u2c42a1b2scf69e83df931035d@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Doug Ledford Cc: Linux RAID Mailing List List-Id: linux-raid.ids On 15/09/2009 18:56, Doug Ledford wrote: > On Sep 10, 2009, at 2:44 PM, Majed B. wrote: >> The maximum throughput you'll get is the PCI bus's speed. Make sure to >> note which version your server has. >> >> The silicon image controller will be your bottleneck here, but I don't >> have any numbers to say how much of a loss you'll be at. You'd have to >> search around for those who already benchmarked their systems, or >> buy/request a card to test it out. > > I've actually been doing some of those benchmarks here. Given a Silicon > Image 3124 card in a x1 PCI-e slot, my maximum throughput should be > about 250MB/s (PCI-e limitation). My drives behind the pm are all > capable of about 80MB/s, and I have 4 drives. What I've found is that > when accessing one drive by itself, I get 80MB/s. When accessing more > than one drive, I get a total of about 120MB/s, but it's divided by > however many drives I'm accessing. So, two drives is roughly 60MB/s > each, 3 drives about 40MB/s each, and 4 drives about 30MB/s each. Were you using a SiI3124-1 (1.5Gbps, they claim 150MB/s) or SiI3124-2 (3Gbps/300MB/s)? What throughput can you get using all 4 channels of the SiI3124 simultaneously, not using the port multiplier - does that top out at 120MB/s too? And have you done similar testing of your port multiplier hanging off a motherboard SATA port? Do you get anywhere nearer the 3Gbps? Just interested... Cheers, John.