[SATLUG] simultaneously burning multiple DVDs

Othniel Graichen othniel at gmail.com
Mon Dec 29 22:38:41 CST 2014


Are you looking for the reason or a solution?
A straight-forward solution is to reduce the Write speed and to use DVD
burners with at least 2MB on-board memory buffers.

The linux cdwriting app is not written/designed to be run in parallel.  It
is designed to compensate for the small buffers on many early drives.
Should the write buffer be depleted while another task is trying to fill the
wrong buffer you have what is called a buffer underrun error.

On Sun, Dec 28, 2014 at 2:58 PM, Borries Demeler <
demeler at biochem.uthscsa.edu> wrote:
>
> On Sun, Dec 28, 2014 at 02:49:12PM -0600, Samuel Smith wrote:
> > On 12/26/2014 12:14 PM, Borries Demeler wrote:
> > >Recently a question has come up for which I do not have a good answer -
> > >does anyone have a good explanation for this:
> > >
> > >If one has multiple DVD writers installed and wants to make multiple
> > >copies of the same iso file by simultaneously writing them to all
> > >installed DVD writers, such an operation produces faulty drives.
> > >Furthermore, K3B does not allow writing to multiple drives - there must
> > >be a reason for that.
> > >
> > >I am trying to figure out where the bottleneck is. Initially, I
> suspected
> > >that the harddrive my not be fast enough to be read by multiple cdrecord
> > >instances. But copying the iso file to a ramdrive and burning with the
> > >ramdrive location as the source offered little to no improvement. The
> > >SATA drives (configured as a RAID) should not be a bottleneck. I
> measured
> > >the sustained read speed to be no less than 150 MB/sec.
> > >
> > >Is there is a solution so one can write to multiple writable DVD drives,
> > >and where is the bottleneck? Does anyone have experience with this
> > >particular problem?
> > >
> > >Thanks, and happy holidays to all! -borries
> > >
> >
> >
> > K3B is basically just a wrapper around several command line tools
> > that burn disks. You could I suppose, just run those commands as
> > many times as needed in parallel. Never tried it though.
> >
> > --Sam
>
> When I said "such an operation produces faulty drives" I meant to say
> faulty DVDs. Those faulty DVDs were created by running multiple instances
> of cdrecord, a commandline tool.  All works well when running one copy,
> but more than one simultaneous burn operation causes the bad DVDs (audio
> skips, for example). The problem gets worse the higher the number of
> simultaneous write operations, even when the source iso file is on a
> ramdrive. Just curious where the bottleneck is and what to do about it.
>
> -b.
> --
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