From mboxrd@z Thu Jan  1 00:00:00 1970
From: Troels Arvin <troels.arvin@gmail.com>
Subject: Shouldn't cache=none be the default for drives?
Date: Wed, 07 Apr 2010 16:39:41 +0200
Message-ID: <4BBC992D.3050905@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
Received: from ge0.mail1.hoer.dk.ip.fullrate.dk ([90.185.1.42]:52242 "EHLO
	smtp.fullrate.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753431Ab0DGOrA (ORCPT <rfc822;kvm@vger.kernel.org>);
	Wed, 7 Apr 2010 10:47:00 -0400
Received: from kurt-III.home.troels.arvin.dk (1608ds2-ksa.0.fullrate.dk [90.184.70.86])
	by smtp.fullrate.dk (Postfix) with ESMTP id AD3189CD4E
	for <kvm@vger.kernel.org>; Wed,  7 Apr 2010 16:39:41 +0200 (CEST)
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Hello,

I'm conducting some performancetests with KVM-virtualized CentOSes. One 
thing I noticed is that guest I/O performance seems to be significantly 
better for virtio-based block devices ("drive"s) if the cache=none 
argument is used. (This was with a rather powerful storage system 
backend which is hard to saturate.)

So: Why isn't cache=none be the default for drives?

-- 
Troels