From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 14 Aug 2001 18:54:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 14 Aug 2001 18:53:57 -0400 Received: from smtp1.one.net ([216.23.22.220]:37126 "HELO us.net") by vger.kernel.org with SMTP id ; Tue, 14 Aug 2001 18:53:46 -0400 Message-ID: <06db01c12514$23afc520$b214860a@amdmb> From: "Ryan Shrout" To: In-Reply-To: Subject: Re: Slow SCSI Disk Access on AMI Elite 1600 controller Date: Tue, 14 Aug 2001 18:54:56 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2919.6700 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > Timing buffered disk reads: 64 MB in 13.92 seconds = 4.60 MB/sec > ... > > 4 - 15K RPM Cheetah SCSI HDDs > > each disks will sustain 30-50 MB/s, so yeah, that's kind of low. > I changed the drives settings from Write-Through to Write-Back and it went to 22.5 MB/sec > > AMI Elite 1600 SCSI RAID controller with 64 MB SDRAM > > I wish people would start with relatively simple controllers, > and only move to fancy ones if they know they need them, > and can prove that the fancy controller works better. > > so for instance, these disks on any PCI ultra2 controller > will easily sustain 100 MB/s. SW raid5 might slow things down > if you had, say, a single celeron (260 MB's dram bandwidth), > but certainly wouldn't effect a dual athlon with ddr. > I am using them in a RAID 0+1 configuration, so this kind of card was needed. Besides, it was a gift (Free!) and I couldn't pass that up. > > Red Hat Linux 7.2 > > do you mean with RH's kernel!?! > No, actually, its 2.4.6-2smp custom compiled. > > So, I then started trying to figure out to raise the buffered disk read > > speed. > > do you have a simple, non-raid ultra2 controller around? > > > My only solution I came across -- find out if the SCSI > > controllers/drives were in asynchronous mode and if they are, change them to > > synchronous mode. > > unless something dramatic is happening, the disks will stay in the > same mode as they're detected at driver-init time, which should be > right before your eyes in /var/log/dmesg. well, at least for a non-fancy > controller. for a gold-plated controller like you have, you need > to find some way to query the controller, perhaps a serial port, > or some too provided by AMI. basically that's a non-linux question, > since the controller has its own little OS that you need to interact with. > > > Now, how can I tell what mode my SCSI disks are in and how can I change it > > to synchronous if it isn't set that way already? > > unless your scsi cabling is utterly botched, they'll be synchronous. > Okay, that helps me so I stop looking for that setting! :) Hopefully, going from 4.5 -> 22.5 MB/sec will be enough to temporarily stop my mysqld crashing. Thanks! Ryan Shrout