From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: weird throughput on write to SATA disk Date: Tue, 14 Oct 2008 18:17:56 +0900 Message-ID: <48F463C4.3070405@kernel.org> References: <1223925629.3947.7.camel@duo> <1223932956.3947.22.camel@duo> <1223936351.3947.41.camel@duo> <1223975694.3947.77.camel@duo> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:38394 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754847AbYJNJT7 (ORCPT ); Tue, 14 Oct 2008 05:19:59 -0400 In-Reply-To: <1223975694.3947.77.camel@duo> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: kenneth johansson Cc: Grant Grundler , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org kenneth johansson wrote: > 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. Can you try deadline scheduler? -- tejun