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, 28 Jan 2001 07:13:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 28 Jan 2001 07:13:16 -0500 Received: from front4m.grolier.fr ([195.36.216.54]:35009 "EHLO front4m.grolier.fr") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Sun, 28 Jan 2001 07:13:09 -0500 Date: Sun, 28 Jan 2001 12:12:17 +0100 (CET) From: Gérard Roudier To: paradox3 cc: linux-kernel@vger.kernel.org, linux-smp@vger.kernel.org Subject: Re: Poor SCSI drive performance on SMP machine, 2.2.16 In-Reply-To: <003f01c088fb$a35c06e0$b001a8c0@caesar> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 28 Jan 2001, paradox3 wrote: > I have an SMP machine (dual PII 400s) running 2.2.16 with one 10,000 RPM IBM > 10 GB SCSI drive > (AIC 7890 on motherboard, using aic7xxx.o), and four various IDE drives. The > SCSI drive > performs the worst. In tests of writing 100 MB and sync'ing, one of my IDE > drives takes 31 seconds. The SCSI drive (while doing nothing else) took > 2 minutes, 10 seconds. This is extremely noticable in file transfers that > completely > monopolize the SCSI drive, and are much slower than when involving the IDE > drives. > After a large data operation on the SCSI drive, the system will hang for > several minutes. > Anyone know what could be causing this? Thanks. > > Attached are some data to help. You didn't provide enough information for anybody to have a single idea about the cause of the problem you report, in my opinion. Just any not too old 10,000 RPM disk is able to sustain more that 25 MB/s sequential data transfer, but cannot do better than 5 milli-seconds latency with random IO patterns. So, result for 100 MB transfer can be less than 4 seconds in the best case but greater than (25000*5)/1000=125 seconds for random 4K IO pattern, for example. What you want to do, in my opinion, could be: - Check in the syslog the actual transfer speed that has been negotiated for your SCSI disk. - Also check if error messages related to disk IOs have been reported by the kernel. - Run some benchmark to check, at least, sequential IO performance (iozone for example will fit) Gérard. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/