From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51561) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dAf1n-00060z-MP for qemu-devel@nongnu.org; Tue, 16 May 2017 12:08:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dAf1j-0005Z0-1U for qemu-devel@nongnu.org; Tue, 16 May 2017 12:08:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48750) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dAf1i-0005XS-Nx for qemu-devel@nongnu.org; Tue, 16 May 2017 12:08:46 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 82A8E7246E for ; Tue, 16 May 2017 16:08:40 +0000 (UTC) References: <20170516111123.17692-1-quintela@redhat.com> <20170516111123.17692-3-quintela@redhat.com> <87shk4g9yb.fsf@dusky.pond.sub.org> <87o9usdg6e.fsf@secure.mitica> <87h90kbxmd.fsf@dusky.pond.sub.org> From: Eric Blake Message-ID: <09f00bd1-df05-c6b3-8423-cb790feddcc2@redhat.com> Date: Tue, 16 May 2017 11:08:35 -0500 MIME-Version: 1.0 In-Reply-To: <87h90kbxmd.fsf@dusky.pond.sub.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="1rC367lEgREvaAPQrhQ4idb9vlHRcngXb" Subject: Re: [Qemu-devel] [PATCH 2/5] migration: Create block capability List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , Juan Quintela Cc: lvivier@redhat.com, qemu-devel@nongnu.org, peterx@redhat.com, dgilbert@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --1rC367lEgREvaAPQrhQ4idb9vlHRcngXb From: Eric Blake To: Markus Armbruster , Juan Quintela Cc: lvivier@redhat.com, qemu-devel@nongnu.org, peterx@redhat.com, dgilbert@redhat.com Message-ID: <09f00bd1-df05-c6b3-8423-cb790feddcc2@redhat.com> Subject: Re: [Qemu-devel] [PATCH 2/5] migration: Create block capability References: <20170516111123.17692-1-quintela@redhat.com> <20170516111123.17692-3-quintela@redhat.com> <87shk4g9yb.fsf@dusky.pond.sub.org> <87o9usdg6e.fsf@secure.mitica> <87h90kbxmd.fsf@dusky.pond.sub.org> In-Reply-To: <87h90kbxmd.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 05/16/2017 11:00 AM, Markus Armbruster wrote: >>>> # periodic mode. (Since 2.8) >>>> # >>>> +# @block-incremental: enable block incremental migration (Since 2.1= 0) >>>> +# >>> >>> What's "block incremental migration" and why should I care? >> >> This is good, I will try. >> >> "block incremental migration assumes that we have a base image in both= >> sides, and then we continue writting in one of the sides. This way we= >> need to only migrate the changes since the previous state where it was= >> the same in both sides". >> >> I am not sure what to put there, really. >=20 > Well, to suggest something, I'd first have to figure out WTF incrementa= l > block migration does. Your text helps me some, but not enough. What > exactly is being migrated, and what exactly is assumed to be shared > between source and destination? >=20 > Block migration is scandalously underdocumented. If I have: base <- active on the source, then: block migration without incremental creates: active on the destination (the entire disk contents are migrated). Conversely, block migration WITH incremental assumes that I have pre-created 'base' on the destination (easy to do, since base is read-only so it can be copied prior to starting the migration), and the migration results in: base <- active on the destination, where only the contents of active were transferred by qemu. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --1rC367lEgREvaAPQrhQ4idb9vlHRcngXb Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJZGyQEAAoJEKeha0olJ0NqrNwH/3NkzoKlNF5odccKgQ5rVO/p WX0uAxrFeVdJbEUv4ij2YzaOat9oRFyUIawG4KNaFOI+99h2eEHlFznwisK08hdO /LAKmSgpWFzCTXMzRlETpNLTGu0BN6coS3soqBlVk1S3tfKD7uAmukskR3cPBe8u 50MDxBW647XkfiQ9fttztdcn33ciOMl09dTmJutnVR0dG2LiDBquDbBlpha6OLjY 3wNu3wKewDi69S3XO8CoJM3cKi4UKtmrla9LzHwqoUOn/XrD7yLJzSRLfI0K4HT1 fBOEIwRarWn5nGC8PDR1AC0BXT24r/vTUedeaokHB8KtYUImd7irq77Flh+Rq7o= =yhm5 -----END PGP SIGNATURE----- --1rC367lEgREvaAPQrhQ4idb9vlHRcngXb--