[mythtv-users] LiveTV glitches at program transitions (was Re: [mythtv] mythplayer.cpp query)

[Michael T. Dean]

On 03/14/2012 08:31 AM, Russell Gower wrote:
>>> I've taken this to the user list as it doesn't appear to be a development issue at this stage.
>>>
>>> After my last post I started digging into the OpenFile() 4014ms issue, as Jens said it appears than the backend is having storage issues, I'm going to setup a separate combinded BE/FE test system for further analysis.
>>>
>>> At this stage I believe the "Waited 0.2 seconds for data" are due to the frontend reading to close to the end of the file, if playback is paused for a few seconds they go away.
>> May as well forward the request over there then...
>>
>> It looks like roughly 7.1 of that 7.6 seconds is sitting there waiting
>> for the data to get written to your filesystem. If the data isn't
>> available for the frontend to read it, then nothing you change in the
>> frontend is going to make the slightest bit of difference. We need to
>> see backend logs to see where the actual stall is.
>>
>> We also need to know more about how your system is actually configured.
>> Looking through the mailing list archives, you appear to be running
>> independent frontends, which means if you are reading off the
>> filesystem, you are reading over NFS. Is it possible your problem is
>> caused by nothing more than NFS caching issues that would be resolved by
>> merely not mounting those disks and letting MythTV stream its content
>> internally?
> I only recently switched to using NFS, as the backend seems to stop supplying data over the internal protocol whilst the scheduler is running, I still had the program transition glitches then as well as additional glitches whenever the scheduler ran.
>
> I no longer have the backend log, but from memory it was the threaded file writer waiting for a flush to finish
>
> My current configuration is rather complicated (two node cluster, with DRBD shared storage etc), i'm in the process of setting up a dedicated system (with a conventional/separate OS/Media disk setup) to do further analysis on - I did had this problem to a lesser extent on my previous system that was a combined FE/BE (with dedicated raid1 disks for recordings) but that was running 0.23.
>
> I currently believe this is a hardware issue, so I will pursue that avenue until I find otherwise.
>
> Thanks to every one that has responded for the feed back, I'll report back my findings for posterity.

Now that I found the thread's new home...

Perhaps you're mounting your NFS file systems without actimeo=0 .

http://www.mythtv.org/docs/mythtv-HOWTO-23.html#ss23.8

Mike