[mythtv-users] mythfilldatabase stunning my system

M. Scott Doerrie mdoerri at cs.jhu.edu
Thu Jan 25 20:28:43 UTC 2007

Greg Foster wrote:
> On 1/24/07, Mike Perkins <mikep at randomtraveller.org.uk> wrote:
>> Greg Foster wrote:
>>> On 1/18/07, M. Scott Doerrie <mdoerri at cs.jhu.edu> wrote:
>>>> I have recently had a similar problem with mythfilldatabase and thought
>>>> I'd share my solution here.  We have a large channel lineup of over 500
>>>> channels -- not that we get all of them, but we like to see them in the
>>>> program guide because we can order them as desired.  Though
>>>> mythfilldatabase may be niced, it is not all that computationally
>>>> expensive.  Rather, the updates are IO intensive, and MySQL attempts
>>>> them as fast as possible.  This interferes with recording and playback,
>>>> causing all manner of visual artifacts.  Sometimes the backend simply
>>>> stops streaming or, less frequently, exits.  I thought that increasing
>>>> the mythbackend ringbuffer would be futile since the updates take well
>>>> over an hour.
>>>> Since the operations are IO bound, I have installed a 4G drive for the
>>>> MySQL database.  The hope was that this would reduce load on the primary
>>>> drive, allowing the backend to continue streaming.  Since it is an older
>>>> drive and can not communicate at the same bus speed as the primary
>>>> drive, I placed it on the secondary ATA bus.  (This bus also contains
>>>> the DVD-RW, but I doubt I'll be watching DVDs at 5 am when I update).
>>>> This solution seems to be working fine.  The frontend will rarely have a
>>>> playback artifact, but they are not present in the recordings.
>>> [snip]
>>> Scott,
>>> Any luck with your changes ?  Seeing the same issues here with a large
>>> lineup, to the point where mythweb doesn't come back with the tv
>>> listings before things time out or get ugly.
>>> _______________________________________________
>>> mythtv-users mailing list
>>> mythtv-users at mythtv.org
>>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>> Possible tangential solution, maybe - move your MySQL database to a
>> different box? Doesn't have to be in the same box as your busy backends.
> Yup.. was just thinking along those lines.  Stumbled across something
> else... mythweb on my frontend only box responds in a reasonable
> amount of time.  I'm starting to suspect my mythweb configuration on
> the backend.  Time to dig and compare ;)
> Greg.
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
Sorry for taking a while to get back.  I've been running this way for a 
couple weeks and everything seems fine.  I pushed the datadirect update 
back to 3 am when I'm usually not watching TV, but sometimes recording  
I've not had any recording issues, and even Live TV seems to be 
alright.  The little 4 GB drive grinds, and since it's on the DVD bus, I 
don't dare watch a DVD at that time.

The above was the final configuration.  In my initial attempt, both the 
primary and sql drives were on the same ATA bus.  This was a failure 
because the small drive was able to starve the large one for bus bandwidth.

I wrote up a "Troubleshooting:Mythfilldatabase IO Bottleneck" topic on 
the MythTV wiki.  I'll update it with howto info later.

Scott Doerrie

More information about the mythtv-users mailing list