Date: Wed, 13 Apr 2005 14:11:39 +0200 From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@DeepCore.dk> To: =?ISO-8859-1?Q?=22Arne_=5C=22W=F6rner=5C=22=22?= <arne_woerner@yahoo.com> Cc: FreeBSD Multimedia <freebsd-multimedia@freebsd.org> Subject: Re: Followup to DVD Burning question Message-ID: <425D0C7B.5070707@DeepCore.dk> In-Reply-To: <20050413115404.34207.qmail@web41203.mail.yahoo.com> References: <20050413115404.34207.qmail@web41203.mail.yahoo.com>
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Arne Wörner wrote: > --- Søren Schmidt <sos@DeepCore.dk> wrote: > >>Arne Wörner wrote: >> >>>That's how I do backups with a DVD-RW: >>> tar cf - ... | dd of=/dev/acd0 obs=32k conv=osync >>> >>>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=a of=/dev/acd0 bs=32k count=1 oseek=10 >>dd if=/dev/acd0 of= /dev/null bs=32k count=1 iseek=10 >>dd if=b of=/dev/acd0 bs=32k count=1 oseek=10 >>dd if=/dev/acd0 of= /dev/null bs=32k count=1 iseek=10 >>dd if=c of=/dev/acd0 bs=32k count=1 oseek=10 >>dd if=/dev/acd0 of= /dev/null bs=32k count=1 iseek=10 > > ... > This looks just like a hard disc to me... I forgot the exact details, but the DVD-RW media (or rather the DVD-RW method of accessing RW media) doesn't allow for non 32K transfers, whereas the DVD+RW method does read-modify-write behind the scene to get it to work seamlessly. I guess this could be worked around in the burner firmware but that would probably offend the DVD consortium ;) -- -Søren
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