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Re: Linux M-Disc support



Sorry for all the typos. I try to run directly on the system console to avoid creating a coaster if SSH decides to hang up. As a result, I couldn't copy-n-paste exactly what happened. I did take pictures on my phone, but apparently didn't copy to the email very well :-(  But many thanks for your help.

On Wed, Jun 29, 2022 at 4:44 AM Thomas Schmitt <scdbackup@gmx.net> wrote:
Hi,

First of all: Congrats to the success and thanks for the report.

I have some comments and corrections for the list archive, though:

Paul von Behren wrote:
> using xorrisofs, copied the ISO using scp to a Ubuntu system
> with the SATA burner, where I used xorisso-as cdrecord.--for_backup

--for_backup has to be used with xorrisofs (the -as mkisofs emulation),
not with xorrecord (the -as cdrecord emulation).
Its purpose is to put an array of MD5 sums to the end of the ISO 9660
filesystem and to add an attribute to each data file which points to
their respective MD5 entry in the array.

Actually xorrecord would refuse on this option:
  xorriso : FAILURE : -as cdrskin: Unknown option '--for_backup'
so i assume that you did it right.

If MD5s were recorded then the -for_backup -check_media run should report
MD5 related messages, like:

  xorriso : UPDATE : Found matching MD5 superblock tag: start=32 size=18
  ...
  xorriso : UPDATE : Found matching MD5 tree tag: start=32 size=9022
  ...
  xorriso : UPDATE : Found matching MD5 session tag: start=32 size=1969789

and at the end of the run

  MD5 checks   :        lba ,       size , result
  MD5 tag range:         32 ,    1969789 , + md5_match

(With multi-session media there are such lines for each session.)


> I then used xoriso check_media_r ... to verify the md5s - all were
> good RC=0.

The proposed xorriso commands are -check_media and -check_md5_r.

There is no -check_media_r. xorriso would refuse:
  xorriso : FAILURE : Not a known command:  '-check_media_r'


> I read a paper that studied failures of burns at various speeds. Even if the
> drive vendor said the drive supported 4x (or faster), the study found much
> fewer failures at slower speed (1x).

My own experience is that healthy drives on healthy media can reliably
write at the maximum speed which they promise. But a BD drive at 10x speed
is a frightening experience.

I have a Pioneer BDR-S09 which rotates so fast when reading BD-RE that
newer Verbatim BD-RE physically break by getting cracks at the rim of
their inner hole. When the crack reaches the dye, the medium becomes
unreadable.
he drive does not react on read speed settings. So the only way to slow
it down is to curb the willingness of xorriso to take data as fast as
the drive delivers them. Therefore i use this xorriso speed setting
command when checkreading BD media by the Pioneer BDR-S09:
  -read_speed soft_force:6xBD
"soft_force:" is quite new. Only the recent version 1.5.4 supports it.


Have a nice day :)

Thomas


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