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Thu, 3 Sep 2020 11:04:55 +0000 (UTC) Subject: Re: [RFC qemu 0/6] mirror: implement incremental and bitmap modes To: =?UTF-8?Q?Fabian_Gr=c3=bcnbichler?= , qemu-devel@nongnu.org References: <20200218100740.2228521-1-f.gruenbichler@proxmox.com> <1599127031.9uxdp5h9o2.astroid@nora.none> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Thu, 3 Sep 2020 13:04:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <1599127031.9uxdp5h9o2.astroid@nora.none> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="hJXcfCH8ATLmS1RqrSpxDRbkKpuB4L54I" Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/03 04:23:49 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -44 X-Spam_score: -4.5 X-Spam_bar: ---- X-Spam_report: (-4.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-2.403, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , John Snow , Markus Armbruster , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --hJXcfCH8ATLmS1RqrSpxDRbkKpuB4L54I Content-Type: multipart/mixed; boundary="avzPtqhIsINHFbmZdhdYwrpnIMb5xrwwY" --avzPtqhIsINHFbmZdhdYwrpnIMb5xrwwY Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 03.09.20 12:13, Fabian Gr=C3=BCnbichler wrote: > On August 21, 2020 3:03 pm, Max Reitz wrote: >> On 18.02.20 11:07, Fabian Gr=C3=BCnbichler wrote: >> >> [Sorry :/] >=20 > same, I've been meaning to ping/pick this back up but other stuff got in= =20 > the way. so thanks for the reminder to get this upstream ;) >=20 >> >>> picking up on John's in-progress patch series from last summer, this is >>> a stab at rebasing and adding test cases for the low-hanging fruits: >>> >>> - bitmap mirror mode with always/on-success/never bitmap sync mode >>> - incremental mirror mode as sugar for bitmap + on-success >>> >>> Fabian Gr=C3=BCnbichler (4): >>> mirror: add check for bitmap-mode without bitmap >>> mirror: switch to bdrv_dirty_bitmap_merge_internal >>> iotests: add test for bitmap mirror >>> mirror: move some checks to QMP >>> >>> John Snow (2): >>> drive-mirror: add support for sync=3Dbitmap mode=3Dnever >>> drive-mirror: add support for conditional and always bitmap sync mode= s >> >> Looks reasonable to me. I would indeed merge patches 2 through 4 into a >> single one, and perhaps switch patches 5 and 6. >> >> Also, we still need an S-o-b from John on patch 2. >> >> I have one question: When the mirror job completes successfully (or is >> cancelled =E2=80=9Csuccessfully=E2=80=9D), the bitmap is always fully cl= eared when the >> job completes, right? (Unless in =E2=80=9Cnever=E2=80=9D mode.) >=20 > I have to take a closer look as well, it's been a while ;) No problem, I=E2=80=99m... *cough* not exactly in a hurry. > IIRC the idea=20 > was that failed mirrors would allow re-using the bitmap for a next=20 > attempt, unless the mode is always. we are not using that feature (yet)= =20 > though (see below). >=20 >> Not that I think we should change the current implementation of =E2=80= =9Cclear >> sync_bitmap; merge dirty_bitmap into sync_bitmap;=E2=80=9D. Just a ques= tion for >> understanding. >> >> >> Soo... What=E2=80=99s the plan? >=20 > I'll rebase, squash as suggested and resend next week! OK :) > I am not sure how=20 > the S-O-B by John is supposed to enter the mix - should I just include=20 > it in the squashed patch (which would be partly authored, but=20 > not-yet-signed-off by him otherwise?)? I=E2=80=99m not too sure on the proceedings, actually. I think it should b= e fine if you put his S-o-b there, as long as your patch is somehow based on a patch that he sent earlier with his S-o-b underneath. But I=E2=80=99m= not sure. > do you pick it up once he's replied with one? Yes, that=E2=80=99s what would be best. > FWIW, with been running with this for quite a while downstream with no=20 > issues, but we are only using the following part: >=20 > - create bitmap(s) > - (incrementally) replicate storage volume(s) out of band (using ZFS) > - incrementally drive mirror as part of a live migration of VM > - drop bitmap(s) >=20 > so no fancy semi-permanent bitmap that gets re-used here. I've been=20 > toying with implementing some sort of generic replication feature akin=20 > to zfs send/recv though, but given that we only have built-in persistent= =20 > bitmaps with qcow2 and the chance of some other tool or the user messing= =20 > up other image formats is high, the safe usage scenarios are a bit=20 > limited. OK. > we do use such long-running bitmaps for our new backup driver though,=20 > and it works quite well there! Good! :) Max --avzPtqhIsINHFbmZdhdYwrpnIMb5xrwwY-- --hJXcfCH8ATLmS1RqrSpxDRbkKpuB4L54I Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl9QzdYACgkQ9AfbAGHV z0CX4gf+OGRQuUNxPYM7wfF7nLt46XjT45IOp8ZcbCpj4mhT+jaWa5rHinSG0hsR QIk52aSJzKC9WFY/38liNbmSZG70kcfGN7ArquYiPun8tLIMyncHYQs1sBdpBGni DagtjTqGXxAf1guRTAAOCways5CBh6i9/JMDL0TaSEp9/tSO7qBJBqjU81qpL1WP 9O6GPxE2FXE5P8hky6NEP6QlxmJASVm4Piu60MkATOC+D+aS/4B4VrOI2uCV32Oi y0rNfNfE/Uw0IxVnUPKuzjV8SJRbX145daZbHN5CG9YLId2ydwjeJXVL9esMSe8m 6XKTOsIqMUlUG0cM+1Wg/uv6wSdOwA== =LLGm -----END PGP SIGNATURE----- --hJXcfCH8ATLmS1RqrSpxDRbkKpuB4L54I--