[mythtv-users] Has anybody put together a three tuner system

Poul Petersen petersp at MATH.ORST.EDU
Tue Jun 10 12:02:52 EDT 2003


	Just as a data point, I'm running MythTV 0.9 (yeah I just
downloaded it!) on RedHat 9 with an AMD XP 2200+. My hard drive 
returns about 53MB/s from hdparm. Even when tuned down to 320x240
resolution with RTJpeg, I get skipping while trying to record 3
programs and watching one of the recordings. The hard drive is
getting pretty beat up, so without actually making a careful analysis
with iostat/sar I think the problem my be device contention.

	With these I get the following:
	
1) Recording two programs:		40% idle CPU
2) Recording two program+LiveTv		30% idle CPU (sometimes <10%)
3) Recording three programs		<10% idle CPU
4) Recording three programs+watch one	0% idle CPU 

	When I reviewed one of the recordings from #3 above, it had some
occassional skipping. When trying to run in type #4, the skipping is
sometimes really bad, other times it is acceptable. It's kinda strange.
I'm not clear on why there is such a discrepancy between #2 and #3 - it
seems like LiveTV should be about the same amount of work as recording
three programs? I would probably get more consisten results from sar
(oh, I did make sure that stuff like updatedb was not running, cause
that one really hurts)

	In any event, with such little overhead to spare, common tasks like
channel changing and skipping forward crawl along (compared to normal). I
probably won't actually run this system with three cards (I just happened to
have three and thought I would try it. Actually, I have four cards, but I'm
obviously not going to bother with that many :) 

-poul


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