From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 6 Jan 2002 20:49:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 6 Jan 2002 20:49:28 -0500 Received: from gear.torque.net ([204.138.244.1]:41739 "EHLO gear.torque.net") by vger.kernel.org with ESMTP id ; Sun, 6 Jan 2002 20:49:11 -0500 Message-ID: <3C38FE40.CF9E84A@torque.net> Date: Sun, 06 Jan 2002 20:47:44 -0500 From: Douglas Gilbert X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.5.2-pre9 i686) X-Accept-Language: en MIME-Version: 1.0 To: elim CC: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: slow scsi disk perf (sym53c875 and IBM drives) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > I've been having relatively poor scsi disk performance > for as long as I can remember now. I've experienced this > with ~2.2.12 all the way up to 2.4.17. > > I'm not much of a scsi buff but I've read some > suggestions such as proper termination, queue depths, > etc but nothing seems to have helped. My understanding > is that I should be getting better performance than I'm > getting with these drives. I have a few DCHS UW disks and get about 10 MB/sec on a streaming read from them (slower toward the end of the disk). You can make your own measurements bypassing the block subsystem (and sd) with the sg_dd utility found in sg3_utils package. That package is now listed on freshmeat.net . For example: $ time sg_dd if=/dev/sg0 of=/dev/null bs=512 count=2M to time a 1GB (approx) read at the start of the disk. [Use sg_map to work out the mapping between the "sd" and "sg" device names.] If there is a major discrepancy between this figure and what you are seeing from hdparm then there is a problem. On the disk in this box (Seagate ST318451LW 15Krpm) I get: hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 64 MB in 1.99 seconds = 32.16 MB/sec In my sg_dd tests I get better than 40 MB/sec. The hdparm test definitely was timing extraneous activity because the disk light was not on all the time. > Any suggestions would be appreciated and if this is not > the right forum to ask.. please direct me to the proper > place. linux-scsi@vger.kernel.org is arguably a more appropriate newsgroup. Doug Gilbert Rest of original post [for the linux-scsi list] vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv hdparm output: /dev/sda: Timing buffered disk reads: 64 MB in 10.94 seconds = 5.85 MB/sec /dev/sdb: Timing buffered disk reads: 64 MB in 8.66 seconds = 7.39 MB/sec /dev/sdc: Timing buffered disk reads: 64 MB in 10.88 seconds = 5.88 MB/sec SCSI subsystem driver Revision: 1.00 sym53c8xx: at PCI bus 0, device 12, function 0 sym53c8xx: setting PCI_COMMAND_PARITY...(fix-up) sym53c8xx: 53c875 detected with Symbios NVRAM sym53c875-0: rev 0x26 on pci bus 0 device 12 function 0 irq 10 sym53c875-0: Symbios format NVRAM, ID 7, Fast-20, Parity Checking sym53c875-0: on-chip RAM at 0xe0502000 sym53c875-0: restart (scsi reset). sym53c875-0: Downloading SCSI SCRIPTS. scsi0 : sym53c8xx-1.7.3c-20010512 sym53c875-0-<0,*>: FAST-10 WIDE SCSI 20.0 MB/s (100.0 ns, offset 15) Vendor: IBM Model: DCHS09W Rev: 6363 Type: Direct-Access ANSI SCSI revision: 02 sym53c875-0-<1,*>: FAST-20 WIDE SCSI 40.0 MB/s (50.0 ns, offset 15) Vendor: IBM Model: DGHS09U Rev: 03E0 Type: Direct-Access ANSI SCSI revision: 03 sym53c875-0-<4,*>: FAST-10 WIDE SCSI 20.0 MB/s (100.0 ns, offset 15) Vendor: IBM Model: DCHS09W Rev: 6363 Type: Direct-Access ANSI SCSI revision: 02 sym53c875-0-<0,0>: tagged command queue depth set to 8 sym53c875-0-<1,0>: tagged command queue depth set to 8 sym53c875-0-<4,0>: tagged command queue depth set to 8 Attached scsi disk sda at scsi0, channel 0, id 0, lun 0 Attached scsi disk sdb at scsi0, channel 0, id 1, lun 0 Attached scsi disk sdc at scsi0, channel 0, id 4, lun 0 SCSI device sda: 17774160 512-byte hdwr sectors (9100 MB) Partition check: sda: sda1 < sda5 sda6 sda7 > SCSI device sdb: 17774160 512-byte hdwr sectors (9100 MB) sdb: sdb1 sdb2 SCSI device sdc: 17774160 512-byte hdwr sectors (9100 MB) sdc: sdc1