From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53215) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQZec-0001Uf-S5 for qemu-devel@nongnu.org; Wed, 06 Jun 2018 10:43:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQZeb-0007MF-Op for qemu-devel@nongnu.org; Wed, 06 Jun 2018 10:43:14 -0400 Date: Wed, 6 Jun 2018 17:43:03 +0300 From: "Michael S. Tsirkin" Message-ID: <20180606173140-mutt-send-email-mst@kernel.org> References: <20180524113251.GB4660@redhat.com> <20180528183058.GG2209@redhat.com> <20180528183833.GJ4580@localhost.localdomain> <20180528212054.GH2209@redhat.com> <20180528212510.GC4660@redhat.com> <20180529064415.GA4756@localhost.localdomain> <2b3eef00-f326-c1e6-0e4b-b7602646eec4@redhat.com> <20180606123237.2235ae4a@kitsune.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] storing machine data in qcow images? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Michal =?iso-8859-1?Q?Such=E1nek?= , Kevin Wolf , "Richard W.M. Jones" , qemu-devel@nongnu.org, stefanha@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, Eric Blake On Wed, Jun 06, 2018 at 01:02:53PM +0200, Max Reitz wrote: > Yeah, but why make qcow2 that format? That's what I completely fail to > understand. Because why not? It's cheap to add it there and is much easier than teaching people about a new container format. Eric Blake put it very well I think. There are several things that several people would like to see addressed: (1) A sensible list of guest visible aspects of the VM preserving which across VM restarts we deem critical enough to support starting guests. At this point this includes at least architecture and machine type. (2) A compact file format for serializing list (1) (3) Ability to store file (2) in a qcow2 image You are asking why store (2) in qcow2 image specifically. The answer is it's just one place where we can store it. The answer is we don't need to involve qemu-block at all for storing it in other places. But for many people it will be handy to have it in the same file, and qcow2 is popular enough that many people will be well served if it's there. -- MT