Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757475AbYJNJPU (ORCPT ); Tue, 14 Oct 2008 05:15:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753076AbYJNJO6 (ORCPT ); Tue, 14 Oct 2008 05:14:58 -0400 Received: from 1-1-4-20a.ras.sth.bostream.se ([82.182.72.90]:57059 "EHLO amd.kenjo.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752479AbYJNJO5 (ORCPT ); Tue, 14 Oct 2008 05:14:57 -0400 Subject: Re: weird throughput on write to SATA disk From: kenneth johansson To: Grant Grundler Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: <1223925629.3947.7.camel@duo> <1223932956.3947.22.camel@duo> <1223936351.3947.41.camel@duo> Content-Type: text/plain Date: Tue, 14 Oct 2008 11:14:54 +0200 Message-Id: <1223975694.3947.77.camel@duo> Mime-Version: 1.0 X-Mailer: Evolution 2.24.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 36 On Mon, 2008-10-13 at 18:33 -0700, Grant Grundler wrote: > On Mon, Oct 13, 2008 at 3:19 PM, kenneth johansson wrote: > ... > >> Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"? > > > > I changed to use O_DIRECT and it's much more consistent now. 69-75 with > > 74 about 95% of the time. > > That's low but it could be worse. Many things can contribute to slow > disks. Well my main problem was that it was fluctuating so much that can't be right. > Favorites are overtemp (See SMART field 194) and vibration (no > measurement possible w/o special equipment). "dd" isn't exactly a > performance application until one uses really big block sizes (1MB or > larger). All my numbers comes from using 1MB blocks. but I'm not using dd. After removing the logic that actually put some data into the buffers I do get about 105 MB/sec using O_DIRECT. I'm doing a full disk write now to get a reference plot. Not using O_DIRECT should be almost identical. > > the disk is supposed to have 105 115 sustained > > data rate. > > Where did 105-115 number come from? datasheet . they listed two drives in the same column so that was not the range it was sustained OD and the model I have max out at 105. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/