[mythtv] innodb vs myism preformance

[Yan-Fa Li]

Daniel Manjarres wrote:
> One difference may be the filesystems we're using. I have ext3 on a 
> 700GB lvm volume. The delays get really bad when deleting more than one 
> show on my system.
> 

Interesting.  I run the db on a separate file system.  You're running
everything on one file system ?  Ext3 is kind of famous for slow deletes
as I remember.  My video is stored on xfs, my database on ext3.  All my
disks are RAID1 arrays with LVM overlays of smaller partitions.  Have 
you tried moving the database to it's own file system separate from your
video ?

 From your description, it seems that mythtv is blocking mysql from 
doing file actions due to your filesystem choice.  This is pretty relevant,
because myisam is file based.  Each table being 3 discrete files, data,
index and meta data.  Innodb is a binary blob and probably does a lot of
caching in memory, deferring writes.  I think this is why your 
performance goes up by switching db.

I would try a couple of things:

	a) move the db files to a separate disk partition, or even as a
	test a different machine and use myisam.
	b) if you can afford the downtime or loss of shows, try
	different filesystem types.  I find xfs to be quite stable
	these days under 2.4.29 and I'm sure 2.6.10 is pretty good
	too.

Good luck,

Yan