From mboxrd@z Thu Jan 1 00:00:00 1970 From: berk walker Subject: Re: RAID-5 streaming read performance Date: Tue, 12 Jul 2005 23:15:53 -0400 Message-ID: <42D48769.2080705@panix.com> References: <874qb14btr.fsf@uwo.ca> <1121220487.5552.34.camel@localhost.localdomain> <87mzorfmdx.fsf@uwo.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87mzorfmdx.fsf@uwo.ca> Sender: linux-raid-owner@vger.kernel.org To: Dan Christensen Cc: mingz@ele.uri.edu, Linux RAID List-Id: linux-raid.ids Dan Christensen wrote: >Ming Zhang writes: > > > >>On Mon, 2005-07-11 at 11:11 -0400, Dan Christensen wrote: >> >> >>>I was wondering what I should expect in terms of streaming read >>>performance when using (software) RAID-5 with four SATA drives. I >>>thought I would get a noticeable improvement compared to reads from a >>>single device, but that's not the case. I tested this by using dd to >>>read 300MB directly from disk partitions /dev/sda7, etc, and also using >>>dd to read 300MB directly from the raid device (/dev/md2 in this case). >>>I get around 57MB/s from each of the disk partitions that make up the >>>raid device, and about 58MB/s from the raid device. On the other >>>hand, if I run parallel reads from the component partitions, I get >>>25 to 30MB/s each, so the bus can clearly achieve more than 100MB/s. >>> >>>[...] >>> >>>System: >>>- Athlon 2500+ >>>- kernel 2.6.12.2 (also tried 2.6.11.11) >>>- four SATA drives (3 160G, 1 200G); Samsung Spinpoint >>>- SiI3114 controller (latency_timer=32 by default; tried 128 too) >>> >>> >>only 1 card? 4 port? try some other brand card and try to use several >>cards at the same time. i met some poor cards before. >> >> > >Yes, one 4-port controller. It's on the motherboard. > >I thought that since I get good throughput doing parallel reads from >the four drives (see above) that would eliminate the controller as the >bottleneck. Am I wrong? > >Dan > > Slavery was abolished in the 1800's. b- >- >To unsubscribe from this list: send the line "unsubscribe linux-raid" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html > >. > > >