From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ge0.mail1.hoer.dk.ip.fullrate.dk ([90.185.1.42]:50651 "EHLO smtp.fullrate.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937130Ab0COXTP (ORCPT ); Mon, 15 Mar 2010 19:19:15 -0400 Received: from arvinserver1.home.troels.arvin.dk (1608ds2-ksa.0.fullrate.dk [90.184.70.86]) by smtp.fullrate.dk (Postfix) with ESMTP id 1B3D39CD1D for ; Tue, 16 Mar 2010 00:19:13 +0100 (CET) Received: from localhost (arvinserver1.home.troels.arvin.dk [127.0.0.1]) by arvinserver1.home.troels.arvin.dk (Postfix) with ESMTP id A336C108124 for ; Tue, 16 Mar 2010 00:19:10 +0100 (CET) Received: from arvinserver1.home.troels.arvin.dk ([127.0.0.1]) by localhost (arvinserver1.home.troels.arvin.dk [127.0.0.1]) (amavisd-new, port 10024) with LMTP id BF+QJbGz78GQ for ; Tue, 16 Mar 2010 00:19:08 +0100 (CET) Received: from kurt-III.home.troels.arvin.dk (kurt-III.home.troels.arvin.dk [192.168.1.9]) by arvinserver1.home.troels.arvin.dk (Postfix) with ESMTP id 0CDBC1080F1 for ; Tue, 16 Mar 2010 00:19:08 +0100 (CET) Message-ID: <4B9EC06E.2000101@arvin.dk> Date: Tue, 16 Mar 2010 00:19:10 +0100 From: Troels Arvin MIME-Version: 1.0 Subject: Re: Does fio write only 0x00s? References: <4B9E9D92.80701@arvin.dk> <20100315212219.GQ5768@kernel.dk> In-Reply-To: <20100315212219.GQ5768@kernel.dk> 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: fio@vger.kernel.org Hello, On Mar 15, Jens Axboe wrote: > By default, fio will at init time randomly fill the buffer of the > allocated IO units. If you are using the sync io engine, then only one > buffer will be allocated and that will be repeatedly written. So yes, > that'll compress very nicely. I'm using libaio. So the data from that shouldn't compress all that much? > You can enable refill_buffers=1 and > that'll cause fio to randomly fill it everytime it's submitted instead. > That should effectively disable compression at the storage end. Turning refill_buffers on or off doesn't seem to make much of a difference when compressing fil's work-file with "gzip -2" (201MB vs 198MB). But perhaps, "gzip -2" still compreses more than one can expect from a storage system? I'm probably missing something. Here's the job description file I'm using (in this case only testing a small amount of I/O; when I was testing the storage systems, I used size=10g and six numjobs=6): =========================================================== [global] description=Emulation of Intel IOmeter File Server Access Pattern [iometer] bssplit=512/10:1k/5:2k/5:4k/60:8k/2:16k/4:32k/4:64k/10 rw=randrw rwmixread=70 direct=1 size=1g ioengine=libaio iodepth=256 refill_buffers=0 =========================================================== -- Regards, Troels Arvin http://troels.arvin.dk/