From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36572) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fRCBU-0006vr-31 for qemu-devel@nongnu.org; Fri, 08 Jun 2018 03:51:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fRCBR-000516-0C for qemu-devel@nongnu.org; Fri, 08 Jun 2018 03:51:44 -0400 Date: Fri, 8 Jun 2018 08:51:37 +0100 From: Stefan Hajnoczi Message-ID: <20180608075137.GD29183@stefanha-x1.localdomain> References: <1487347224-8667-1-git-send-email-pl@kamp.de> <20170220145011.GJ21255@stefanha-x1.localdomain> <73412b92-353d-7109-cfbe-9c61bf91e7eb@kamp.de> <20180607101046.GC19032@stefanha-x1.localdomain> <2ddb8b13-650a-5bd7-8c77-3f2eca34efdf@virtuozzo.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="PHCdUe6m4AxPMzOu" Content-Disposition: inline In-Reply-To: <2ddb8b13-650a-5bd7-8c77-3f2eca34efdf@virtuozzo.com> Subject: Re: [Qemu-devel] [Qemu-block] [RFC PATCH V4] qemu-img: make convert async List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy Cc: Peter Lieven , kwolf@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com --PHCdUe6m4AxPMzOu Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jun 07, 2018 at 01:19:29PM +0300, Vladimir Sementsov-Ogievskiy wrot= e: > 07.06.2018 13:10, Stefan Hajnoczi wrote: > > On Fri, Jun 01, 2018 at 07:16:14PM +0300, Vladimir Sementsov-Ogievskiy = wrote: > > > 20.02.2017 17:59, Peter Lieven wrote: > > > > Am 20.02.2017 um 15:50 schrieb Stefan Hajnoczi: > > > > > On Fri, Feb 17, 2017 at 05:00:24PM +0100, Peter Lieven wrote: > > > > > > this is something I have been thinking about for almost 2 years= now. > > > > > > we heavily have the following two use cases when using qemu-img > > > > > > convert. > > > > > >=20 > > > > > >=20 > > > [...] > > >=20 > > > > > Does this patch work with compressed images?=A0 Especially the > > > > > out-of-order write mode may be problematic with a compressed qcow2 > > > > > image. > > > > It does, but you are right, out-of-order writes and compression sho= uld > > > > be mutually exclusive. > > >=20 > > > Sorry for being late, but can you please explain to me, why? > > There are image format-specific limitations on compressed writes. For > > some reason I thought they were append-only in qcow2, but I was wrong. > >=20 > > Stefan >=20 > And what are limitations for compressed writes in qcow2? Writes must be cluster-aligned and the size must be 1 cluster (except for the last cluster in an image). qemu-img convert honors this, so it's not a problem. > We can't write asynchronously? Why? Async compressed writes are supported nowadays. I think my original comment was wrong. It should be fine to use out-of-order compressed writes. Stefan --PHCdUe6m4AxPMzOu Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAEBAgAGBQJbGjWJAAoJEJykq7OBq3PIWZgIALncLtu+SvGG+seICTN9v0Id PAZvatH2bn0dIuLiOsZ75iXbPiiOT617icuL0jz5oYi8pNTB5k/KqGghmlQNYpQh tA5fvwGMyUBPn2yjY9bHniVi+ZB0xFLNg38oNi+XNifizl+g4h1WOR/qTcwGIkb1 f+CtYU4P8sXfrzIARd/DsdaFYa13qgbqmtV6qiGTFaIhd9I+5fshAtFG4pQOMgm5 L0akQEDA1uCQqMBIpgbUSblCNU9EsNWRh483+SH959YLe3gFQAF/rqYhfypbTQWS 1b4bxJWSqHoVxwB9SrCT3sZXZPLXuLkvPuf/pMNeyoTjPV9nLf+hWxZ2ZX9lx6A= =pMHj -----END PGP SIGNATURE----- --PHCdUe6m4AxPMzOu--