From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36070) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQX0T-0007Ij-7H for qemu-devel@nongnu.org; Wed, 06 Jun 2018 07:53:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQX0S-0004jW-Cy for qemu-devel@nongnu.org; Wed, 06 Jun 2018 07:53:37 -0400 References: <20180528183058.GG2209@redhat.com> <20180528183833.GJ4580@localhost.localdomain> <20180528212054.GH2209@redhat.com> <20180528212510.GC4660@redhat.com> <20180529064415.GA4756@localhost.localdomain> <2b3eef00-f326-c1e6-0e4b-b7602646eec4@redhat.com> <20180605092159.GA2544@work-vm> <46ef4200-eccf-7e65-d3a0-69e4a7414b51@redhat.com> <20180606111406.GD2660@work-vm> <20180606114228.GH1455@redhat.com> <20180606114817.GC3064@redhat.com> From: Max Reitz Message-ID: Date: Wed, 6 Jun 2018 13:53:27 +0200 MIME-Version: 1.0 In-Reply-To: <20180606114817.GC3064@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="3dtDjy1nXg3AZ5lAtgfhnbVyj4HLeD2af" Subject: Re: [Qemu-devel] storing machine data in qcow images? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , "Richard W.M. Jones" Cc: "Dr. David Alan Gilbert" , Kevin Wolf , qemu-block@nongnu.org, "Michael S. Tsirkin" , qemu-devel@nongnu.org, armbru@redhat.com, stefanha@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --3dtDjy1nXg3AZ5lAtgfhnbVyj4HLeD2af From: Max Reitz To: =?UTF-8?Q?Daniel_P._Berrang=c3=a9?= , "Richard W.M. Jones" Cc: "Dr. David Alan Gilbert" , Kevin Wolf , qemu-block@nongnu.org, "Michael S. Tsirkin" , qemu-devel@nongnu.org, armbru@redhat.com, stefanha@redhat.com Message-ID: Subject: Re: [Qemu-devel] storing machine data in qcow images? References: <20180528183058.GG2209@redhat.com> <20180528183833.GJ4580@localhost.localdomain> <20180528212054.GH2209@redhat.com> <20180528212510.GC4660@redhat.com> <20180529064415.GA4756@localhost.localdomain> <2b3eef00-f326-c1e6-0e4b-b7602646eec4@redhat.com> <20180605092159.GA2544@work-vm> <46ef4200-eccf-7e65-d3a0-69e4a7414b51@redhat.com> <20180606111406.GD2660@work-vm> <20180606114228.GH1455@redhat.com> <20180606114817.GC3064@redhat.com> In-Reply-To: <20180606114817.GC3064@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 2018-06-06 13:48, Daniel P. Berrang=C3=A9 wrote: > On Wed, Jun 06, 2018 at 12:42:28PM +0100, Richard W.M. Jones wrote: >> On Wed, Jun 06, 2018 at 12:14:07PM +0100, Dr. David Alan Gilbert wrote= : >>> The problem with having a separate file is that you either have to co= py >>> it around with the image or have an archive. If you have an archive >>> you have to have an unpacking step which then copies, potentially a l= ot >>> of data taking some reasonable amount of time. Storing a simple bit >>> of data with the image avoids that. >> >> This isn't really true. For OVA (ie. tar) we don't unpack them. >> Adding file.offset and file.size in qemu's raw driver was crucial to >> that optimization. >=20 > Though that assumes you're only using the qcow2 file in read-only mode.= > As soon as you need write access you need to unpack from the OVA so tha= t > the qcow2 file can grow its length when new sectors are allocated. Except if the qcow2 file is at the end of the archive. Then all you need to do is adjust the length field of the tar file header. Max --3dtDjy1nXg3AZ5lAtgfhnbVyj4HLeD2af Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAlsXyzgACgkQ9AfbAGHV z0DqYQgAnadwiG8H79CKbqCeGIp5vHZsujhUGxch0q16CDCcrJo+BP2WTfcE9xK8 Vp6Q0RHEJpIyEr6N/tSm1WyYeU9g+ZwNYzfTGsDxhOEAcSU28cdYAf0GoN82kst4 2Ur1MlfC1DMmK6lNSNVu+hOa4jkqB5i6mL8zmSumf++wslSMwF303YgQPNbPt0Y6 natwzjmAUH/cVWBIcTzFzyQ9ADphkDds3Jf70Hmg0atzwFebm66T8LBVt+SegRWU ZQiOW+DdEufS4n+Pku6CMgDCt+/uNi1nj2woJzTWI8JlxRp8V0I4ArK9m+vlgKwI rAt2XwkDe7SFMjEcH3nYA274k8Yntg== =R/Tq -----END PGP SIGNATURE----- --3dtDjy1nXg3AZ5lAtgfhnbVyj4HLeD2af--