[mythtv] mythconverg on RAM drive?

Jack Perveiler perveilerj at yahoo.com
Thu Aug 3 13:10:35 UTC 2006

> if you're having issues with MySQL taking too long, i suggest you first look
> at converting those tables from MyISAM to InnoDB.
> for many kinds of tables, InnoDB can be anywhere between 1.5x to 30x
> 'faster' -- _particularly_ when there are SQL 'DELETE' operations involved.

InnoDB also has the advantage of having the actual db rows kept in memory by
mysql.  mysql only caches myisam indexes and lets the filesystem handle the row
caching, but with innodb you can tell mysql how much mem to allocate for the
rows (I think the parameter was something like "buffer_pool_size").

I have a gig of ram, but when recording a number of high-bitrate programs the
filesystem cache filled up with recording data.  Going to disk to get the db
was causing me IOBOUND errors (this was back before Daniel vastly improved on
the IOBOUND errors in general), despite having all that ram.  Moving to innodb,
giving mysql something like a 300 meg buffer_pool, and turning my kernel
swappiness way down made a world of difference.  Everything from starting to
view a recording to scheduler re-schedules just became much snappier
(previously my disk would grind when starting either of those).

I imagine this is one of those "your milage my vary" issues, but it certainly
helped my situation.  And having mysql handle the syncing to disk seems a lot
more safe than managing ramdisk-to-disk syncs on your own.


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