From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:53886) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghHDl-0000ns-Ck for qemu-devel@nongnu.org; Wed, 09 Jan 2019 12:00:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghHDk-0007yk-Ha for qemu-devel@nongnu.org; Wed, 09 Jan 2019 12:00:49 -0500 References: <20190108194552.45453-1-vsementsov@virtuozzo.com> <20190109112311.GB4867@localhost.localdomain> <5ddd78e0-90ed-a6e5-c454-f1a2e44c1a37@redhat.com> <20190109165111.GI4867@localhost.localdomain> From: Eric Blake Message-ID: <9efd0cd9-1f2e-4f99-4f2a-93919756493f@redhat.com> Date: Wed, 9 Jan 2019 11:00:31 -0600 MIME-Version: 1.0 In-Reply-To: <20190109165111.GI4867@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="akLu5MXyd3lH6cTkmcLD1tBDwfrh15idx" Subject: Re: [Qemu-devel] [PATCH] file-posix: add rough-block-status parameter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf , Paolo Bonzini Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org, armbru@redhat.com, mreitz@redhat.com, fam@euphon.net, stefanha@redhat.com, den@openvz.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --akLu5MXyd3lH6cTkmcLD1tBDwfrh15idx From: Eric Blake To: Kevin Wolf , Paolo Bonzini Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org, armbru@redhat.com, mreitz@redhat.com, fam@euphon.net, stefanha@redhat.com, den@openvz.org Message-ID: <9efd0cd9-1f2e-4f99-4f2a-93919756493f@redhat.com> Subject: Re: [PATCH] file-posix: add rough-block-status parameter References: <20190108194552.45453-1-vsementsov@virtuozzo.com> <20190109112311.GB4867@localhost.localdomain> <5ddd78e0-90ed-a6e5-c454-f1a2e44c1a37@redhat.com> <20190109165111.GI4867@localhost.localdomain> In-Reply-To: <20190109165111.GI4867@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 1/9/19 10:51 AM, Kevin Wolf wrote: > Am 09.01.2019 um 17:42 hat Paolo Bonzini geschrieben: >> On 09/01/19 12:23, Kevin Wolf wrote: >>> Also note that this is only metadata preallocation; full preallocatio= n >>> will still return allocated for the protocol layer and so it will alw= ays >>> be slow. >> >> Full preallocation these days can create images with preallocated but >> known-zero blocks, I think? >=20 > That would defeat one of the main purposes of preallocation because it > would still require COW and metadata updates on the first write. >=20 > If there is demand, we could add something like preallocation=3Ddata wh= ere > data clusters are preallocated but COW/metadata updates still happen at= > runtime, but so far nobody has asked for it. Not sure when you would us= e > it either. Except there HAS been talk about it before - such a mode makes it so that you can guarantee a non-fragmented image, or even guarantee that the entire guest-visible portion is contiguous and all qcow2 metadata is at the front or back of the overall qcow2 file, making it very easy to convert between qcow2 -> raw (strip the qcow2 metadata) or go in reverse (wrap a raw into a qcow2) without having to shuffle the guest-visible portions of the file. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --akLu5MXyd3lH6cTkmcLD1tBDwfrh15idx Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEY3OaSlgimHGqKqRv3g5py3orov0FAlw2KK8ACgkQ3g5py3or ov1n1Af/U+sqluN+vcuwyWraBFe2CuPRnh7noKDZD3hKnveemPVNuunl2NZ/HaDA Kw/QvuCDcUfYUmFNqye5t4Oo35qsm02/I8C7Dzio2ODY448NTh3MD/lkZ9OJRibs OUtS/BFxV9Q+qZMtAattD+feRZqJ9HBVbuXeqvFAF6qym5atPwwI9XMf9bgBvroz ziclkRdipYwpkvxT82odvmFJpdjbO7+CCC0J1vrfOZVYvSS69Ndntv++uQ8vLJQr b9BUnmOELdVpz/93XrU92L6PaQzG1qYvVbcQMAAW6hDgFST6IMU7HiQU3L2bEA8r PhiEC3Xqd8AVcmfT319km6UUhDZ9WA== =nTbP -----END PGP SIGNATURE----- --akLu5MXyd3lH6cTkmcLD1tBDwfrh15idx--