From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:51599) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TbVRt-0004fv-6A for qemu-devel@nongnu.org; Thu, 22 Nov 2012 07:00:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TbVRm-0004Hy-VA for qemu-devel@nongnu.org; Thu, 22 Nov 2012 07:00:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:22093) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TbVRm-0004Hs-N8 for qemu-devel@nongnu.org; Thu, 22 Nov 2012 06:59:58 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id qAMBxw9v023582 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 22 Nov 2012 06:59:58 -0500 Date: Thu, 22 Nov 2012 12:59:55 +0100 From: Stefan Hajnoczi Message-ID: <20121122115955.GB13571@stefanha-thinkpad.redhat.com> References: <1353504237-5608-1-git-send-email-kwolf@redhat.com> <1353504237-5608-3-git-send-email-kwolf@redhat.com> <20121121151408.GB22778@stefanha-thinkpad.redhat.com> <50ACF19F.5000102@redhat.com> <20121122073754.GB7398@stefanha-thinkpad.redhat.com> <50ADEB76.8060807@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50ADEB76.8060807@redhat.com> Subject: Re: [Qemu-devel] [PATCH 2/2] Documentation: Update image format information List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org On Thu, Nov 22, 2012 at 10:08:06AM +0100, Kevin Wolf wrote: > Am 22.11.2012 08:37, schrieb Stefan Hajnoczi: > > On Wed, Nov 21, 2012 at 04:22:07PM +0100, Kevin Wolf wrote: > >> Am 21.11.2012 16:14, schrieb Stefan Hajnoczi: > >>> On Wed, Nov 21, 2012 at 02:23:57PM +0100, Kevin Wolf wrote: > >>>> @item qed > >>>> -Image format with support for backing files and compact image files (when your > >>>> -filesystem or transport medium does not support holes). Good performance due > >>>> -to less metadata than the more featureful qcow2 format, especially with > >>>> -cache=writethrough or cache=directsync. Consider using qcow2 which will soon > >>>> -have a similar optimization and is most actively developed. > >>>> +Old QEMU image format. Left for compatibility. > >>>> + > >>>> +For new images, use qcow2 instead. You might want to consider using the > >>>> +@code{lazy_refcounts=on} option to get a more QED-like behaviour. > >>> > >>> The first sentence should be kept, it describes the general feature set > >>> and scope of this image format. I agree that the rest of the paragraph > >>> can be dropped. > >>> > >>> You could insert a statement saying that qcow2 is now preferred because > >>> it is actively developed and offers advanced features and performance as > >>> the very first sentence. > >> > >> It's the same terse description as for qcow1. If we decided to describe > >> the format in more detail, we should do so consistently, and probably > >> also for non-native formats. (But why? The only use case is > >> compatibility with other/older hypervisors, which is mentioned.) > > > > Yes, we should have descriptions of other formats too. > > > > Users dealing with existing guests using these formats should still have > > access to general information about the formats. For example, if I'm a > > new user and it's my job to work with an existing qcow1 disk image then > > it's not very helpful to just see a terse "Use qcow2 instead" message. > > > > It's not good to drop documentation on a feature because it is > > deprecated. > > I can see your point, but the whole section starts to become a bit > lengthy then for a man page. Also, I don't think that your qcow1 user > really needs a detailed description - he already has a format and > doesn't have to choose one, so the characteristics aren't that > important. If he considers converting the image, we're back to raw and > qcow2. > > Maybe we should keep the current descriptions for raw and qcow2 (as they > are what users really choose between for new images), and extend and > move the documentation of other formats into qemu-doc.texi and mention > them in the man page of qemu-img only as "Also supported for > compatibility with other hypervisors or older QEMU versions: vmdk, vdi, > qed, ... See the QEMU Emulator User Documentation for more information > on these." Sounds good. Stefan