From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Grant Grundler" Subject: Re: weird throughput on write to SATA disk Date: Mon, 13 Oct 2008 14:07:15 -0700 Message-ID: References: <1223925629.3947.7.camel@duo> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-out.google.com ([216.239.33.17]:55421 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755251AbYJMVHu (ORCPT ); Mon, 13 Oct 2008 17:07:50 -0400 In-Reply-To: <1223925629.3947.7.camel@duo> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: kenneth johansson Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, Oct 13, 2008 at 12:19 PM, kenneth johansson wrote: > When writing data to /dev/sdb (that is the whole disk and no filesystem) > it starts out ok around 100MB/sec but soon end up doing considerably > worse. For prolonged times lasting several minutes it hovers in the > 20-30MB/sec. Is the application using "O_DIRECT"? If not, could be issue with how VM writeback is (not) working. Can you reproduce this using fio or even "dd"? (See git://git.kernel.dk/fio) grant > > This happens on two different SATA disk one samsung and one seagate and > on both 2.6.26 and 2.6.27 kernel. The disk are connected to the external > esata connector. Controller is 00:1f.2 SATA controller: Intel > Corporation 82801HB (ICH8) 4 port SATA AHCI Controller (rev 02) > > What could be the reason for this ?? reading is no problem. > > >