From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38901) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGpdi-0005Zk-Er for qemu-devel@nongnu.org; Wed, 06 Jan 2016 10:04:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aGpde-0003cb-Eb for qemu-devel@nongnu.org; Wed, 06 Jan 2016 10:04:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42094) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGpde-0003cT-8s for qemu-devel@nongnu.org; Wed, 06 Jan 2016 10:04:38 -0500 References: <6ca84848.f052.15211b20317.Coremail.magazine.lihuiba@163.com> <568BCB6C.7010709@redhat.com> <557a47a5.3564.15214d76e2e.Coremail.magazine.lihuiba@163.com> From: Eric Blake Message-ID: <568D2D00.3050600@redhat.com> Date: Wed, 6 Jan 2016 08:04:32 -0700 MIME-Version: 1.0 In-Reply-To: <557a47a5.3564.15214d76e2e.Coremail.magazine.lihuiba@163.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wmmhanBkQKce6KpW4Euo3ApOW416UEg0t" Subject: Re: [Qemu-devel] qcow2 snapshot + resize List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: lihuiba Cc: "qemu-devel@nongnu.org" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --wmmhanBkQKce6KpW4Euo3ApOW416UEg0t Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 01/05/2016 07:50 PM, lihuiba wrote: > At 2016-01-05 21:55:56, "Eric Blake" wrote: >> On 01/05/2016 05:10 AM, lihuiba wrote: >> >>>>> In our production environment, we need to extend a qcow2 image with= >>>>> snapshots in it. >> >>>> The thing is that one would need to update all the inactive L1 table= s. I >>>> don't think it should be too difficult, it's just that apparently so= far >>>> nobody ever had the need for this feature. >> >> Is resizing a snapshot really what you want? Ideally, a snapshot trac= ks >> the data from a point in time, including the metadata of the size bein= g >> tracked at that time. Extending the snapshots then reverting to that >> snapshot means your guest would see a larger disk on revert than it di= d >> at the time the snapshot was created, which guests might not handle ve= ry >> well. > I want to make resizing (extending only) and snapshot independent to ea= ch other,otherwise going back and forth in snapshots may cause the disk s= hrinked and extended. That would introduce some technical trouble, and po= ssibly confuse user as well. If I take a snapshot while the guest sees a 1G disk, then resize the disk to 2G, then roll back to the point in time of the snapshot, I'd expect the disk to roll back to 1G in size. Anything else is likely to confuse the guest. And that's what current resize support already does (it only resizes the active image, not the snapshots). --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --wmmhanBkQKce6KpW4Euo3ApOW416UEg0t 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/ iQEcBAEBCAAGBQJWjS0BAAoJEKeha0olJ0NqZZYIAKd8VH0nTHoC37NPI1+tsiMm F2Wxq4Gz7j8AKBLJkfzMD0HV5LeLCIGGaFda5Stc3Eq9yiaLg120V2YbiMf2T+U0 CqX+1iRUbdw0NY04/3RKYWWh1LcN4Ll3e5nPOzD1T+rF9rJpfuOqI8MMYHcxjFxz c+2l7X6nfxIvCt23wjnAUvF85Bp4KEDGQ0HSlYCcvx6WXmvp8qUmHtXayeg2Jccd s8YbQCwDwGxTaldQWU7tcrh4X2dhr/zaVfEvsahI6JaoxCvUtqpSIJh5s2J1R53m 9rpq82ddXs6bJDN7YMIOWk1/JU0GHRP+E9d96XqcCBGPQKit62DGsRx0Rb8xqEA= =i5AX -----END PGP SIGNATURE----- --wmmhanBkQKce6KpW4Euo3ApOW416UEg0t--