From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 8 Dec 2001 16:33:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 8 Dec 2001 16:33:33 -0500 Received: from tomts5.bellnexxia.net ([209.226.175.25]:51194 "EHLO tomts5-srv.bellnexxia.net") by vger.kernel.org with ESMTP id ; Sat, 8 Dec 2001 16:33:21 -0500 Message-ID: <3C11358D.28400117@sympatico.ca> Date: Fri, 07 Dec 2001 16:33:01 -0500 From: Chris Friesen X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.16 i686) X-Accept-Language: en MIME-Version: 1.0 To: "linux-kernel@vger.kernel.org" Subject: software raid issues -- possible kernel I/O problem? 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 just installed some new ata100 hard drives and matching controller card in a machine running 2.4.16, and have been experimenting with software raid. I've run into some interesting issues with regards to transfer speeds. I've got md0 as a raid0, and md1 as a raid1. hda is an older ata33 drive connected as master to the motherboard, while hde and hdg are the new ata100 drives each connected as master on one of the two channels on the adapter (but the adapter only has one IRQ, so I don't know how that will affect things...). Using hdparm, I get the following results: md0: 98.46/42.67 md1: 98.46/29.22 hda: 98.46/9.1 hde: 97.71/31.37 hdg: 96.24/30.92 I also tried some simultaneous runs, with results as follows: hde and hdg: 50.20/23.27 and 53.56/21.77 hde and hda: 50.59/29.09 and 55.90/9.17 So, my observations are as follows: 1) It seems as though I can't get aggregate burst speeds up above about 100MB/s no matter what I do, even when it's on separate interfaces with separate IRQs. Is this running into the limitation of the PCI bus? I'm also somewhat confused as to how my old ata33 drive managed to score nearly 100MB/s burst speed, as well as how some people are claiming scores of 160MB/s on a ata100 drive (and why I'm not getting that on mine). 2) Similarly, actual read speads appear limited to an agregate of about 45MB/s in both the raid-0 and simultaneous runs. Why am I not getting twice the throughput of the single drive case? Could this be due to the ata100 controller only using a single IRQ? 3) It doesn't appear as though raid-1 reads are being parallelized. This surprised me, as I thought that raid-1 was supposed to come close to raid-0 in terms of read performance. Anyone have any ideas about why this isn't happening? I'd appreciate any comments you have, or if this isn't the right place to talk about this, then a redirection to the appropriate forum. Thanks, Chris