From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Fehlig Subject: Re: [PATCH] vhd-util create: add -C|nocow option Date: Thu, 21 Nov 2013 17:57:38 -0700 Message-ID: <528EAC02.9010009@suse.com> References: <1385019976-19885-1-git-send-email-cyliu@suse.com> <1385026779.6071.112.camel@kazak.uk.xensource.com> <21134.7091.735293.78218@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <21134.7091.735293.78218@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Jackson Cc: xen-devel@lists.xensource.com, Ian Campbell , Chunyan Liu List-Id: xen-devel@lists.xenproject.org Ian Jackson wrote: > Ian Campbell writes ("Re: [Xen-devel] [PATCH] vhd-util create: add -C|nocow option"): > >> On Thu, 2013-11-21 at 15:46 +0800, Chunyan Liu wrote: >> >>> Add '-C' (nocow) option to vhd-util create. >>> >>> Btrfs has terrible performance when hosting VM images, even more when the guest >>> in those VM are also using btrfs as file system. One way to mitigate this bad >>> performance is to turn off COW attributes on VM files (since having copy on >>> write for this kind of data is not useful). According to 'chattr' manpage, NOCOW >>> could be set to new or empty file only on btrfs, so add a option here so that >>> users could have a chance to set NOCOW to a vhd image. >>> >> Is there not some btrfs (or generic) utility which could be used to do >> this after image creation rather than trying to build it in to every >> utility which creates an image file? >> > > This may seem like a daft question, but why do we even have a vhd > utility in our tree ? Is there not some vhd tools package that this > should be in ? > Newer qemu-img supports vhd and vhdx right? Is there even a need for this tool at all anymore? Regards, Jim