From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Heflin Subject: Re: How to boost performance Date: Thu, 17 Jun 2010 17:25:03 -0500 Message-ID: <4C1AA0BF.6030300@gmail.com> References: <20100617100109.32a20ffa@natsu> <20100617221300.3e30afe0@natsu> <4C1A50FA.50504@stud.tu-ilmenau.de> <38599704579ec5d844bada876838dda7.squirrel@www.dcsnow.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <38599704579ec5d844bada876838dda7.squirrel@www.dcsnow.com> Sender: linux-raid-owner@vger.kernel.org To: aragonx@dcsnow.com Cc: st0ff@npl.de, linux-raid@vger.kernel.org List-Id: linux-raid.ids On 06/17/2010 02:51 PM, aragonx@dcsnow.com wrote: >> Actually, you have not said a word about which controllers you use (for >> the drives). Using the wrong controller can drain speed a lot. As from >> the kernel benchmarks it seems like neither RAM nor computing power are >> the bottlenecks. >> >> Some SATA-controllers handle "nearly parallel" writes to multiple drives >> better than others. SiI products for example have a noticeable drop-off >> for each disk you add. Pretty late Intels nearly show no impact of many >> disks in parallel. So maybe that could be the topic you should be >> after. (And maybe a lspci could help :) >> >> Stefan > > Hi Stefan, > > Here is the output of lspci. There are 5 disks on the ATI controller. > Four of them are part of the RAID. The last disk is on the JMicron > controller which is a PCIE-1x card. I can move one more disk to the > JMicron controller if you think that would help. Or just purchase a new 4 > port controller? > > lspci|grep SATA > 00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller > [IDE mode] > 02:00.0 SATA controller: JMicron Technologies, Inc. 20360/20363 Serial ATA > Controller (rev 03) > > --- > Will Y. > > [IDE mode] is probably a bad idea...a bios setting will change that. Mine shows this: 00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller [AHCI mode] And my results on similar test show this (3x500gb raid5), single disk shows this speed, so raid write speed breaks down to about 60-70% of single disk speed: dd if=/dev/sdb of=/dev/null bs=1M count=2048 2048+0 records in 2048+0 records out 2147483648 bytes (2.1 GB) copied, 28.8118 s, 74.5 MB/s dd if=/dev/zero of=zerofile bs=1M count=2048 conv=fdatasync,notrunc 2048+0 records in 2048+0 records out 2147483648 bytes (2.1 GB) copied, 36.6523 s, 58.6 MB/s dd if=/dev/zero of=zerofile bs=1M count=6144 conv=fdatasync,notrunc 6144+0 records in 6144+0 records out 6442450944 bytes (6.4 GB) copied, 113.893 s, 56.6 MB/s dd if=/dev/zero of=zerofile bs=1M count=16384 conv=fdatasync,notrunc ^C15006+0 records in 15006+0 records out 15734931456 bytes (16 GB) copied, 277.814 s, 56.6 MB/s And this for reads: dd if=zerofile of=/dev/null bs=1M count=6144 conv=fdatasync,notrunc 6144+0 records in 6144+0 records out 6442450944 bytes (6.4 GB) copied, 53.8029 s, 120 MB/s