Last night I was playing with my MythTV box setting up a frontend on my MacBook and I noticed after I was done playing that the MythTV backend server's disk was constantly making noise. When I stopped the MythTV backend services, the noise stopped. Then once I started it back up the activity continue the way it was before. After doing a little Googling, I found out that others had had this problem on Ubuntu 8.04 shortly after installing MythTV. Later in the bug report someone discovered that on their machine, the constant disk activity was MythTV logging that it couldn't connect to the MySQL server. Turns out they were exactly right. In my /var/log/mythtv/mythbackend.log file, it was constantly writing:

QSqlQuery::exec: database not open QSqlQuery::exec: database not open 2009-06-26 23:50:02.359 DB Error (KickDatabase): Query was: SELECT NULL; No error type from QSqlError? Strange... QSqlQuery::prepare: database not open QSqlQuery::exec: database not open 2009-06-26 23:50:02.412 DB Error (SimpleDBStorage::load()): Query was: SELECT station FROM record WHERE recordid = :WHERERECORDID No error type from QSqlError? Strange... 2009-06-26 23:50:02.413 Unable to connect to database! 2009-06-26 23:50:02.414 Driver error was [1/1045]: QMYSQL3: Unable to connect Database error was: Access denied for user 'mythtv'@'localhost' (using password: YES)

Turns out, I had been messing with the MySQL permissions to get my MythTV frontend machine to work and hadn't noticed that I broke the backend. If you install MythTV and notice that you get constant disk access after it starts, this is likely the culprit.