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Date: Wed, 13 Apr 2005 14:11:39 +0200
From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@DeepCore.dk>
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Subject: Re: Followup to DVD Burning question
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Arne W=F6rner wrote:
> --- S=F8ren Schmidt <sos@DeepCore.dk> wrote:
>=20
>>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.
>>
>=20
> Why? I can read and write the same block of a DVD-RW round robin.
> I mean:
>=20
>>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
>=20
> ...
> This looks just like a hard disc to me...

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 =

it to work seamlessly. I guess this could be worked around in the burner =

firmware but that would probably offend the DVD consortium ;)

--=20

-S=F8ren