From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.parallels.com ([64.131.90.16]:46631 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051Ab2FLBIV (ORCPT ); Mon, 11 Jun 2012 21:08:21 -0400 Received: from [199.115.105.252] (helo=mail.parallels.com) by mx2.parallels.com with esmtps (TLSv1:AES128-SHA:128) (Exim 4.77) (envelope-from ) id 1SeFam-0001vM-VE for linux-btrfs@vger.kernel.org; Mon, 11 Jun 2012 21:08:21 -0400 Message-ID: <4FD69681.4000404@parallels.com> Date: Tue, 12 Jun 2012 10:08:17 +0900 From: dima MIME-Version: 1.0 To: Subject: Re: KVM on top of BTRFS References: <1339456922.32583.YahooMailNeo@web160802.mail.bf1.yahoo.com> In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 06/12/2012 08:53 AM, Alex wrote: > Matthew Hawn yahoo.com> writes: >> What are the recommendations for running KVM images on BTRFS systems using > kernel 3.4? I saw older >> posts on the web complaining about poor performance, but I know a lot of work > has gone into btrfs since then. >> There also seemed to be the nocow option, but I didn't find anything that > said it actualy helped. I don't think it is about the kernel version, but rather about choosing the right option for KVM. I am running KVM via libvirt on btrfs with lzo compression, autodefrag, inode and space cache for quite some time. Yes, I did set nocow for the directory with images. I have no proof that it actually helps with disk images, but being set for the build directory my build time is down 5 minutes. I used raw virtio images with no caching. I guess this is the key if we talk about disk I/O. The performance looks fine, though I only use it for testing. The last time I tried to install WinXP on KVM it was a disaster. But I guess I did not choose the right options, nor did I install virtio drivers inside the guest. VirtualBox still outperforms KVM on btrfs in my view. best