[mythtv-users] Better listings for Schedules Direct users. Free! (was Re: another scheduling strangeness/question)

Michael T. Dean mtdean at thirdcontact.com
Wed Sep 1 20:56:33 UTC 2010


  On 09/01/2010 04:18 PM, Gabe Rubin wrote:
> On Wed, Sep 1, 2010 at 1:07 PM, Michael T. Dean wrote:
>> Also, I highly recommend running optimize_mythdb.pl on a daily basis.  It
>> may not help /that/ much, but it shouldn't hurt.
> This brings up another question I have.  I have cron jobs to optimize
> and backup the database daily.  Does it matter which goes first (i.e.,
> is it possible that optimizing could damage the database so I would
> want a backup prior to that operation)?

That's kind of a chicken-and-egg problem.  It's possible that repairing 
(which is one of the things optimize_mythdb.pl does) a crashed table 
could cause damage or data loss (especially if there's a mysqld crash 
while repairing a table, but data loss is actually possible even without 
the crash).  That said, if you have any crashed tables, those tables 
can't be backed up to a SQL-based backup.  So, when you have a crashed 
table, you can't back up the database because of the crashed table***.  
But, if you repair the table, it can cause damage or data loss (though 
the likelihood of either is rather small).

So, basically, when you get to the point where data loss is most likely 
to occur--when you have a crashed table--the most important backup is 
yesterday's backup.  The mythconverg_backup.pl script will actually keep 
around older backups, rotating them out as new are created.  This means 
that when you lose a table today, you have yesterday's backup to save you.

That said, I've been running optimize_mythdb.pl daily since it was first 
committed and haven't had any problems with it.  I do back up the 
database with the mythconverg_backup.pl script, so that helps me to 
worry less.  :)

Mike

***Or, at least, you'd have to tell mysqldump not to back up the crashed 
tables--in which case you're not backing up the crashed table, which is 
the one most likely to undergo loss.


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