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Re: How to "blank" / "zero out" / "nullify" a dvd-rw?

"Thomas Schmitt" <scdbackup@gmx.net> wrote:

> Hi,
> > I'm trying to "blank" / "zero out" / "nullify" a dvd-rw that has
> > previously had data written to it, so that I can give that dvd-rw to
> > someone else and they wont see the data. (NB I'm _not_ worried about
> > "magnetic/optical history", the FBI, the CIA etc).
> > Please note that I DO NOT necessarily want to turn the disk back to
> > the way it was when it was still in its plastic wrapper.
> > ...
> > ~# growisofs -Z /dev/hdc=/dev/zero
> > ...
> > :-[ WRITE@LBA=0h failed with SK=5h/ASC=30h/ACQ=05h]: Wrong medium type
> > :-( media is not formatted or unsupported.
> > :-( write failed: Wrong medium type
> > ...
> > ~$ dvd+rw-mediainfo
> > ...
> >  Mounted Media:         14h, DVD-RW Sequential
> You got a sequentially written DVD-RW.
> Before you can overwrite its content it needs to be blanked 
>   dvd+rw-format -blank=full /dev/hdc
> or formatted
>   dvd+rw-format -force /dev/hdc


If the media was written in the default (reliable) sequential
mode, you only need to call cdrecord blank=fast

A full blank is only needed if the media was written in packet mode
before or if it was formatted.

> On occasion of anniversary of libburn revival let me state

Well, cdrecord will soon have it's 10th DVD writing anniversary ;-)

> Blanking but not formatting can be done with cdrecord and wodim
>    cdrecord -v dev=ATA:1,0,0 blank=all

This is not needed.....

cdrecord usually works without dev= parameter. If you need it because
you have more than one drive, dev=ATA:1,0,0 will not work.

Then you should call cdrecord -scanbus and the most possible
parameter is dev=1000,0,0

>    wodim    -v dev=/dev/hdc  blank=all

Let me not comment non-free software...

> > But (and this is the strange part), if I format the disk using
> > "dvd+rw-format -blank=full /dev/hdc" (which works), then "growisofs -Z
> > /dev/hdc=/dev/zero" works perfectly THE FIRST TIME - it only fails the
> > second time I try to do it.
> That's because unformatted DVD-RW are much like CD-RW.
> You can write a session to them, leave them open, append
> another session, and so on. But you can re-use them only
> after blanking.
> dvd+rw-format -blank=full brings a DVD-RW into this
> unformatted state. -blank without "=full" does the same as
> cdrecord blank=fast. 

It is most unlikely that dvd+rw-format -blank=full does the same
as cdrecord blank=fast. This would be counter-intuitive.

> > is there a way to "blank" / "zero out" / "nullify" 
> > a dvd-rw which won't permanently destroy the
> > disk if I do it 20 times?
> (start sarkasm) To my experience, most DVD-RW are destroyed
> before they get into their shrink wrap. (end sarkasm)

DVD-RWs last a very long time if you use the right software, e.g. cdrecord.

> Formatting is needed only once. The media stays overwriteable
> until you deformat it or it finally refuses to work with
> your drive. So there is no problem with 20 times or so.

Formatting DVD-RWs will take them into a less reliable mode.

> Blanking (i.e. deformatting) seems not to be more dangerous
> to the media than overwriting with data. This way or that
> way the media will give up its life early enough.
> I got 3 DVD burners and none of them works well with 4x DVD-RW.

DVD-RWs are very reliable. DVD+RW is a mess, I found no drive that
realiably reads DVD+RWs written by drives from another brand.

Be sure to prefer cdrecord blank=fast over cdrecord blank=all


 EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
       js@cs.tu-berlin.de                (uni)  
       schilling@fokus.fraunhofer.de     (work) Blog: http://schily.blogspot.com/
 URL:  http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily

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