Re: Burning and mounting written BDs

[Thomas Schmitt]

Hi,

Kjetil Kjernsmo wrote:
> xorriso -outdev /dev/sr0 -blank as_needed -map [...]

With the next burn run i would insert command -for_backup before -outdev
in order to get MD5 checksums recorded for the data files and the overall
session. These checksums can be used by xorriso command -check_media when
there is doubt about correctness of reading.

(Nomenclature: The arguments of xorriso are "commands" not "options",
because their sequence matters much. It's more like shell commands in
a script than options like with a run of program "tar".)


> ISO image produced: 23090263 sectors

So this is a "50 GB" double layer medium. Expensive already without "M".

(I recently bought 5 BD-RE DL and already the first one caused trouble in
my drives. Only one of three wanted to format the medium. In the end the
power supply of a USB box died after 40 GB of writing. This might be an
unrelated coincidence, but i refrain from making more experiments until
i was able to find a compatible 2000 mA power dumpling to fill up the
ranks of my hardware zoo.)


> Disk state:       incomplete

This just means that the medium was not closed by xorriso and could
take more data. If you next time want to close the media, add xorriso
command -close "on" to the commands of the burn run.


> root@robin:/dev# mount -t iso9660 -o nodev,noexec,nosuid,ro,sbsector=0 
> '/dev/sr0' '/mnt/test/'
> mount: /mnt/test: wrong fs type, bad option, bad superblock on /dev/sr0,
> [...]
> [4683501.642523] isofs_fill_super: bread failed, dev=sr0, iso_blknum=16, 
> block=16

This means that the drive has problems to read data from the start of the
filesystem. That's normally not a problem of the burn software but of
the relation between drive and medium: either at burn time or at read
time.

The specific error reason might be given in following lines of the system
log.
But for our purpose it is better to let xorriso try reading and hopefully
get original error information from the drive:

  xorriso -for_backup -indev /dev/sr0 -check_media -- 2>&1 | tee -i 
/tmp/xorriso_log

This run will normally not abort on the first encountered read error but
will try to read on. If slow progress and repeated error messages indicate
that reading is futile, then end the run by Ctrl+C or by creating the
file  /var/opt/xorriso/do_abort_check_media  .

If the emerging log file  /tmp/xorriso_log  appears to be too long for
list posting, send it to me in private for examination:
  scdbackup@gmx.net
I will then post the relevant parts and my diagnosis.


> root@robin:/dev# xorriso -dev /dev/sr0 -mount indev auto auto /mnt/test/
> [...]
> xorriso : NOTE : Loading ISO image tree from LBA 0
> [ snip ]
> xorriso : UPDATE :   40115 nodes read in 9 seconds

This does not look too bad. xorriso was obviously able to read the blocks
which the kernel failed to read. Since both use the same SCSI commands
for reading, it is well possible that this time mounting would have
succeeded.

I am really curious what a -check_media run finds by reading the whole
written range of the medium.


> [...]
> xorriso : FAILURE : -mount: image-to-disk features are not enabled by option
> -osirrox

To successfully use the xorriso -mount command, the command -osirrox "on"
needs to be given first or you need to run xorriso as its alter ego
"osirrox":

  osirrox -indev /dev/sr0 -mount indev auto auto /mnt/test/

Further xorriso will probably need superuser powers to finally execute the
Linux mount command.

In the end that mount command would not do anything different then your
mount attempt as superuser, which ended by the "iso_fill_super" read
error.
So given falure and success on the same medium, it seems that the relation
between drive and medium is not very stable.


> This is on brand new media, and M-discs are really expensive, so they ought
> to be top-of-the-line...

Well, it's about both, drive and medium. We'll see.


> And the price makes me reluctant to resort to too much
> trial-and-error too.

For now we have the written medium for examination.

Depending on the outcome, it might be worth to try single-layer BD-R
with that drive or to use non-M-Disc BD-R DL of which you make
one or more identical copies. But let's first examine the written medium
before making plans for future writing.


Have a nice day :)

Thomas