[SATLUG] simultaneously burning multiple DVDs

Kevin Buckner sirjaggy29 at gmail.com
Sun Dec 28 21:05:11 CST 2014


Maybe the bottleneck is the controller chipset for the DVD writer. This may
use a limited buffer to spool the data to write from and is not designed
for multiple devices. The DVD system software maybe the bottleneck because
it can handle one write at a time.
On Dec 28, 2014 8:49 PM, "Borries Demeler" <demeler at biochem.uthscsa.edu>
wrote:
>
> On Sun, Dec 28, 2014 at 08:08:47PM -0600, Christopher Chavez 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.
> >
> > The bottleneck could be in how the DVD writers are connected. If I'm not
> > mistaken you have only mentioned how the hard drives were connected,
and I
> > would agree that it is not a bottleneck in this instance.
> > How are the DVD drives connected? Depending on the burning speed, I've
read
> > that an interface like a single PATA/IDE channel shared between two
drives,
> > especially without an 80 conductor cable, or USB 2.0 DVD writers
connected
> > through a hub, can lead to burn failure from buffer underrun. Some
> > drives/programs have an option to try using "buffer underrun protection"
> > provided by the DVD writer; in cdrecord (a.k.a. wodim, which are used
by K3B),
> > this had to be enabled manually in older versions (driveropts=burnfree)
but it
> > is now enabled by default. Some BIOSes have options that prevent
PATA/IDE from
> > operating at the highest speeds supported by the drives, so those may
also be
> > checked.
>
> I am aware of the limitations with PATA connected drives, especially if
> they are on the same cable. All the drives here are modern, high speed
> SATA drives. This is a modern 6-core AMD system with 16 GB RAM that
> should be generously enough configured for burning 4 disks simultaneously.
>
> > I'm not certain this always works, but probably the only workaround if
the
> > DVD writer's interface is simply too slow is to force burning at a
lower speed
> > (wodim speed=#). I think another way to possibly detect bottlenecks is
to try
>
> That's a thought, and I will try this, even though it would sort of
defeat the purpose.
>
> > benchmarking the read speed from the burners individually and/or
> > simultaneously; this may identify a safe upper burning speed.
> > Cf. http://en.wikipedia.org/wiki/DVD#Transfer_rates and
> > http://en.wikipedia.org/wiki/List_of_device_bit_rates
>
> Interesting, the system bus for the board and the SATA drives should be
more than
> sufficient to support this, so I am still baffled where the bottleneck is,
> Is there another bus that would be involved?
>
> Thanks, -Borries
> --
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