From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sm02.isp.telecom.li ([217.173.238.131]:51405 "EHLO sm02.isp.telecom.li" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751229AbaCQUOP (ORCPT ); Mon, 17 Mar 2014 16:14:15 -0400 Message-ID: <5327577B.8050703@adon.li> Date: Mon, 17 Mar 2014 21:13:47 +0100 From: jvogt MIME-Version: 1.0 Subject: Re: correct file size to use References: <53243539.5010405@adon.li> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Ming Lei , Matthew Eaton , fio@vger.kernel.org, Carl Zwanzig Am 17.03.2014 03:55, schrieb Ming Lei: > On Mon, Mar 17, 2014 at 7:16 AM, Matthew Eaton >> Tested on my system and saw no difference in performance. Direct io >> will bypass the page cache so the only thing that comes to mind would > Looks I miss the '--direct=1' parameter, :-( > >> be an on-device cache, though, I would think the difference in >> performance would be more dramatic if that were the case. > Another possible cause might be related with storage for the > big file. If the file is stored in lot of fragments of the disk, accessing > the whole file might become slower than just the first 10M, but not > sure if there is so big difference(30%). > Direct io will bypass the page cache so the only thing that comes to mind would be an on-device cache, though, I would think the difference in performance would be more dramatic if that were the case. This could be possible - I'm not so sure how to check that... My setup is the following: RHEL6.5 as virtual machine via VMWare - the storage is a Dell Equallogic Storage connected via ISCSI to the host. These tests are not made via NFS. I just wanted to make some tests before taking it all in production. Thank you all for your answers! Josef