Re: Can t blank BD-RE disc?

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> Once again, it seems xorriso is to the rescue:

I like your attitude towards xorriso, but in
this case there is a misunderstanding:

BD-RE do not get blanked like CD-RW or DVD-RW.
xorriso just tries to handle all media types
uniformly under the premise that ISO 9660
filesystems shall to be their content.

It presents BD-RE in a very similar way as BD-R
but that is an artificial emulation. The first
ISO 9660 session and the update "sessions" get
arranged on the random-access media in a
recognizable chain of mountable images.
This works with plain files or USB sticks, too.

So this is emulated:

> Media status : is written , is appendable
> Media summary: 1 session, 12075457 data blocks, 23.0g data, 25.1m free

Not much room to add more sessions, but it
would have worked.


> $ xorriso -dev /dev/sr1 -blank "deformat"
> [..about 15 seconds passes..]
> Media status : is blank
>
> Does such a short blanking time seem to be correct?  It takes much
> longer to fully blank even a CD-RW disc, for example.

This just defaced the existing ISO 9660
filesystem PVD (a part of the equivalent of a
super block).

The 15 seconds were needed to read a few kB from
media, to replace two byte by 'X', and to write
the few kB back to media.

You will now get from:
  dd if=/dev/sr1 bs=2048 skip=16 count=1 | \
  od -c | \
  head -1
something like
  0000000 001   C   D   X   X   1 ...more bytes...
whereas you see in a valid ISO filesystem
  0000000 001   C   D   0   0   1 ...more bytes...


You may as well be brutal and bonk 64 kB of
zeros onto the start of the media:

  dd if=/dev/zero of=/dev/sr1 bs=64K count=1

As you can see, you don't need a burn program
for BD-RE. They are just much too slow for normal
filesystems. The wear patterns of sequential 
archivers or burn programs are more appropriate
for them.


Have a nice day :)

Thomas