From owner-freebsd-current@FreeBSD.ORG Mon Sep 13 09:42:58 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id BF2F516A4CE for ; Mon, 13 Sep 2004 09:42:58 +0000 (GMT) Received: from spider.deepcore.dk (cpe.atm2-0-53484.0x50a6c9a6.abnxx9.customer.tele.dk [80.166.201.166]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1AEDF43D5C for ; Mon, 13 Sep 2004 09:42:58 +0000 (GMT) (envelope-from sos@DeepCore.dk) Received: from [194.192.25.143] (laptop.deepcore.dk [194.192.25.143]) by spider.deepcore.dk (8.12.11/8.12.10) with ESMTP id i8D9guw9083523; Mon, 13 Sep 2004 11:42:56 +0200 (CEST) (envelope-from sos@DeepCore.dk) Message-ID: <41456B73.9000701@DeepCore.dk> Date: Mon, 13 Sep 2004 11:42:11 +0200 From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= User-Agent: Mozilla Thunderbird 0.7.2 (X11/20040802) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Frode Nordahl References: <4142D833.4060802@DeepCore.dk> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable cc: current@freebsd.org Subject: Re: Promise PDC20267 ATA RAID, poor write performance X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Sep 2004 09:42:58 -0000 Frode Nordahl wrote: > On Sep 11, 2004, at 12:49, S=F8ren Schmidt wrote: >> pizzabox# dd if=3D/dev/zero of=3Dfill bs=3D1m count=3D2000 >> 2000+0 records in >> 2000+0 records out >> 2097152000 bytes transferred in 122.908771 secs (17062672 bytes/sec) >=20 > I have done some more test now, reseated cables, disabling other IDE=20 > controllers etc. to no avail. I have tested both drives against the ICH= 2=20 > controller with very good results. >=20 > After some fooling around I found the following: > ar0: ATA RAID1 subdisks: ad4 ad6 status: READY > # dd if=3D/dev/zero of=3Dfill bs=3D1m count=3D100 > 100+0 records in > 100+0 records out > 104857600 bytes transferred in 29.298259 secs (3578970 bytes/sec) > # atacontrol detach ata2 > # dd if=3D/dev/zero of=3Dfill bs=3D1m count=3D100 > 100+0 records in > 100+0 records out > 104857600 bytes transferred in 3.080246 secs (34041957 bytes/sec) >=20 > (this also works when writing 2GB...) >=20 > That is, whenever I run with a single disk or a degraded RAID transfer = > speeds are ok. I have tried this both ways, so it is not one of the=20 > disks / cables that is broken. As soon as I rebuild the RAID again,=20 > write speeds drop to 3MB/s. >=20 > Any ideas as of how to debug this? Sounds strange indeed, there is some performance degradation to be=20 expected from RAID1 (you have to write to both disks) but nothing that=20 ruins performance this badly. I cannot reproduce it no matter what I=20 try, so I'm pretty sure the reason should be found outside ATA. It could be because the two channels are competing for the PCI bus and=20 the arbitration of that fails so you get alot of PCI retries, that is=20 outside ATA's reach to control.. -S=F8ren