[TriLUG] cdrecord reader process chokes?

[Brian Henning]

Hi List,
   Lately I've seen some odd behavior when using cdrecord.  The upshoot 
is, I've had to turn on BURN-Free, which I've not had to use before on 
this computer.

What happens is, the on-drive buffer happily stays up at or near 100% 
for about the first 100MB of any image I'm burning, and then like 
clockwork it dwindles down to zero percent; if BURN-Free isn't turned 
on, at that point there will be a fatal buffer underrun.

What confuses me is, if the burn speed is too high (hovering around 
20x), the buffer should never stay at 100% at all.  So it seems like the 
reader process keeps up perfectly for about the first 100MB, and then 
inexplicably can't supply new data fast enough to keep the buffer filled 
after that.

The burner is a SONY DVD-RW/CD-RW DW-D22A, alone on an IDE channel.
The source HD is a 7200 rpm device on an SATA controller.
The host system is my trusty twin Xeon running Debian Sarge, 2.6.10 SMP.

Any ideas what might be causing this?  BURN-Free successfully prevents 
underruns 9 times in 10 (although interestingly, cdrecord reports that 
it was "never needed" although I can watch the burn speed plummet when 
the buffer gets near empty), but I'd like to not have to use it.

Thanks y'all,
~Brian