[mythtv-users] VDPAU playback stuttering when XvMC playback is just fine?

Andrew Burgess aab at cichlid.com
Sat May 2 14:31:05 UTC 2009


On Sat, 2009-05-02 at 07:12 -0700, Dave Johansen wrote:

> > Run mythbackend as normal. Start watching a show on the frontend as
> > normal - when the skipping starts - run iostat -x on the backend to
> > check util %.
> >
> So I just tried watching a recording of SNL while not recording
> anything and the util% bounces around 98% and will occasionally hit
> 100%.
> 
> But I've record 2 shows before while watching something so I wondered
> how that works. I then set it to record a show and the util% was
> basically 0% with occasional spike to 1 or 2%.
> 
> If I changed to Watch TV and watched that show, then the util% bounced
> between 10 and 35% but was usually in the 15-20% range.
> 
> So then I tried watching that same episode of SNL while the recording
> was happening and the util% hung out at around 5-10%.

One thing that's different is the recording is happening to a different
part of the disk each time.

I had a WD disk recently that was really slow writing but only
sometimes. It brought my entire raid array to a crawl. I noticed it by
running atop (just a more visual way of running iostat). When I failed
the disk and ran the array degraded everything was fine. I RMAed it and
the replacement works fine. (this is the short version of the story, it
took me a while to find the problem :-).

I think the disk firmware just tried too long to recover bad sectors.
Some drive manufacturers offer a special 'raid friendly' firmware
version that fails quicker so the whole array doesn't stall.

So for your case, can you use a spare/different disk just for recordings
and see if that clears things up? 

HTH



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