[mythtv] mythconverg on RAM drive?

Steven Adeff adeffs.mythtv at gmail.com
Fri Aug 4 19:22:29 UTC 2006


On 8/3/06, Jack Perveiler <perveilerj at yahoo.com> wrote:
> >
> > 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.
>
> --Jack


I've found at times (like when in the Watch Recordings screen) where
my wa% is quite high but my recordings drive is not anywhere near the
read or write speeds I've seen the RAID array acheive before, though
the system drive where my sql files are is high (though not that high
from what I would figure).  I've also seen this happen randomly at
other times, and MythWeb seems excruciatingly slow to bring up the
Recorded Programs page. So perhaps its just MySQL processing things...

Jack, how do I convert to InnoDB, etc?

Thanks!
(and sorry for having this on dev, but like I said in the OE, no one
there had any thoughts)

-- 
Steve
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