[Pkg-opt-media-team] Bug#709971: dvd+rw-tools: growisofs more then 1 Bluray, since Debian 7 speed collapses

[Thomas Schmitt]

Hi,

> eject: Kann nicht auswerfen! Letzter Fehler: Unpassender IOCTL
> (I/O-Control) für das Gerät

Jetzt duerfen wir raten, was das fuer ein Fehler war ...
(= Now we may guess what error this was ...)

Google brings me to

#define ENOTTY          25      /* Not a typewriter */

Whatever, a rejected ioctl is quite probably a matter of the kernel.


> Read Test with dd:
> same Work on two drives:
> and on four:

Looks unsuspicious.


> I don't think on the linux cache? Should I?

Depends on how much RAM your machine has.
But the speeds of the already used drives did not increase from
two-drive run to four-drive run.
So i assume the cache did not buffer the whole 650 MB chunks.


> I see the :-[ CLOSE SESSION Bug every Time.

It is said to be harmless (and was promised to get fixed in
growisofs 7.1).
Well, i though you might perhaps use BD-RE.


> if read [via ioctl(SG_IO)] is fast then writing [via ioctl(SG_IO)]
> is slow if writting is fast then read is slow

Somehow simultaneously emitted ioctl(SG_IO) seem to disturb
each other.


> are there hints for Kernel tuning?

I am not a kernel expert (still on 2.6) and to my experience it
is not easy to get support for kernels which are old enough for
being in Debian Stable.

You would probably have to install a current kernel and check
whether the problem persists.


We could watch libburn trying to perform read and write runs while
being disturbed by other instances of libburn.

Writing:

  xorriso -scsi_log on \
          -as cdrecord -v dev=/dev/srX filename.iso \
  2>&1 | tee -i /tmp/xorriso_write_log

Reading:

  time xorriso -scsi_log on \
               -outdev /dev/srX \
               -check_media use=outdev min_lba=0 max_lba=320000 -- \
  2>&1 | tee -i /tmp/xorriso_read_log

There will be measurements of execution time for each command.
Like:

  READ(10)
  28 00 00 00 01 60 00 00 20 00
      16 ms

The log will be very verbous and thus needs to be caught in a
file. Maybe it is necessarey to replace
  2>&1 | tee -i /tmp/xorriso_write_log
by
  > /tmp/xorriso_write_log 2>&1
in order to avoid slowdown by the mass of terminal output text.

Probably you should send it directly to me and not to the
Debian bug tracker. I will then report whether insight could
be gained.


Have a nice day :)

Thomas