[mythtv-users] Strange Issue with Myth and HDHomeRun

[f-myth-users at media.mit.edu]

Where exactly is your database?

As a PVR-x50 user who's been getting screwed for a year by glitches
caused by MySQL locking winding up locking out other table accesses,
this is a sore spot.

I'm assuming that the HDHR isn't trying to write into recordedmarkup
or its SVN incarnation (unlike the ivtv-based encoders), but I'm
wondering if perhaps there's something wrong with your database
(like crashed or extremely un-optimized tables) that's either causing
outright disk contention, or lots of swapping that is itself screwing
your ability to write to disk.  So you might try repairing and
optimizing tables (if you don't already) and see if that helps.

And of course the FE makes large transient demands on the database,
hence my suspicion.  Is your DB on the master backend's CPU?  Same
disk, or a different disk?  (In -my- case, of course, it made no
difference, since it was the DB locking itself that was a problem and
not contention for disk bandwidth, but this wasn't obvious for most of
a year.)  Is your backend swapping a lot?  Can you try moving your
database to a completely different machine to run a test?

(You can accomplish this latter, essentially, by shutting down MySQL,
copying its files to some other machine -with a compatible version-
installed [don't recklessly switch MySQL versions if you're just
copying raw database files w/o import/export!], and changing the
config file on your backend to point to whichever host now has the DB.)

P.S.  If your test system is using the MySQL server on your production
backend, of course, you're splitting things off in a way that might
cause the test system to work fine while the production machine is
encountering contention issues...