Date: Wed, 13 Apr 2005 16:09:15 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: =?iso-8859-1?Q?S=F8ren?= Schmidt <sos@DeepCore.dk> Cc: FreeBSD Multimedia <freebsd-multimedia@freebsd.org> Subject: Re: Followup to DVD Burning question Message-ID: <20050413230915.GA20498@odin.ac.hmc.edu> In-Reply-To: <425D0C7B.5070707@DeepCore.dk> References: <20050413115404.34207.qmail@web41203.mail.yahoo.com> <425D0C7B.5070707@DeepCore.dk>
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--UugvWAfsgieZRqgk Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 13, 2005 at 02:11:39PM +0200, S=F8ren Schmidt wrote: > Arne W=F6rner wrote: > >--- S=F8ren Schmidt <sos@DeepCore.dk> wrote: > > > >>Arne W=F6rner wrote: > >> > >>>That's how I do backups with a DVD-RW: > >>> tar cf - ... | dd of=3D/dev/acd0 obs=3D32k conv=3Dosync > >>> > >>>Unluckily my DVD-RW's cannot be used for UFS with my > >>>burner... I do not know why. > >> > >>DVD-RW doesn't quite cut it for UFS, you need DVD+RW media for > >>that. > >> > > > >Why? I can read and write the same block of a DVD-RW round robin. > >I mean: > > > >>dd if=3Da of=3D/dev/acd0 bs=3D32k count=3D1 oseek=3D10 > >>dd if=3D/dev/acd0 of=3D /dev/null bs=3D32k count=3D1 iseek=3D10 > >>dd if=3Db of=3D/dev/acd0 bs=3D32k count=3D1 oseek=3D10 > >>dd if=3D/dev/acd0 of=3D /dev/null bs=3D32k count=3D1 iseek=3D10 > >>dd if=3Dc of=3D/dev/acd0 bs=3D32k count=3D1 oseek=3D10 > >>dd if=3D/dev/acd0 of=3D /dev/null bs=3D32k count=3D1 iseek=3D10 > > > >... > >This looks just like a hard disc to me... >=20 > I forgot the exact details, but the DVD-RW media (or rather the DVD-RW=20 > method of accessing RW media) doesn't allow for non 32K transfers,=20 > whereas the DVD+RW method does read-modify-write behind the scene to get= =20 > it to work seamlessly. I guess this could be worked around in the burner= =20 > firmware but that would probably offend the DVD consortium ;) One could write a GEOM that did read-modify-write to do blocksize translation. :-) -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 --UugvWAfsgieZRqgk Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFCXaaaXY6L6fI4GtQRAjVKAKCWvndHo8faaYLKBOY+WVzo0gt72wCfQBQP +glMAq7Sv8mBZ7DsAUPfThc= =YiNs -----END PGP SIGNATURE----- --UugvWAfsgieZRqgk--
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