From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mxi1.enovance.com ([94.143.114.217]:17174 "EHLO mxi1.enovance.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751886AbaEGIah convert rfc822-to-8bit (ORCPT ); Wed, 7 May 2014 04:30:37 -0400 Message-ID: <5369E886.1030100@enovance.com> Date: Wed, 07 May 2014 10:02:14 +0200 From: Erwan Velu MIME-Version: 1.0 Subject: Re: Fio giving iops results that are equal to RAM speeds References: In-Reply-To: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" Content-Transfer-Encoding: quoted-printable Sender: fio-owner@vger.kernel.org List-Id: fio@vger.kernel.org To: Kim Holmebakken Cc: fio@vger.kernel.org Le 07/05/2014 09:45, Kim Holmebakken a =EF=BF=BDcrit : > Hey, > > Im currently working on a bachelor thesis where I need to measure iops=20 > on my storage solution. > > I have set up a "frontend" server(ubuntu server 13.10) which has zfs=20 > on linux running, and is connected to an iSCSI RAID(SAN). > > When I use this command: > > fio --directory=3D/pool --size=3D128M --direct=3D0 --fallocate=3Dnone=20 > --rw=3Drandrw --refill_buffers --norandommap --randrepeat=3D0=20 > --ioengine=3Dsync --bs=3D4k --rwmixread=3D100 --iodepth=3D16 --numjobs=3D= 16=20 > --runtime=3D60 --group_reporting --name=3D4krandreadtest [...] > These values are extremly high and I suspect that these are the RAM=20 > speed being returned to me. > > Is there anyway to get a more realistic result? You do cached IOs (as direct=3D0), only 128M of data and everything into a = file. As a result, yes everything is getting into the host's cache. If you want to determine the ISCSI performance byitself, I suggest not=20 using file but the block device and do direct IOs (direct=3D1). If you want to keep your filesystem you have two options : enabling the=20 direct=3D1 and/or making IOs at twice the size of your host memory. Hope this helps, Erwan