[mythtv-users] SchedulesDirect timing out during Mythfilldatabase

David McMillan mythtv at davidmcmillan.com
Sat Jul 23 21:58:41 UTC 2011

On Mon, Apr 18, 2011 at 11:02 AM, Rob Smith <kormoc at mythtv.org> wrote:

> On Mon, Apr 18, 2011 at 6:29 AM, Mark Lord <mythtv at rtr.ca> wrote:
> > But in the end, it just might be mysql doing an excessive number of
> "fsync()"
> > or "fdatasync()" calls.  Databases like to do things that way, but it
> does
> > mean they run very slowly when updating stuff
> I wouldn't call myisam's usage of fsync excessive... I'd call it
> majorly lacking.
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I've been researching this problem and appear to have gotten better
performance by adding the barrier=0 option to the line in /etc/fstab that
mounts the ext4 volume containing the mythconverg database.  My
understanding is that you need to ensure that you don't have power blips
(use a UPS) when disabling write barriers.  I'm also using LVM.

My per/schedule day process times in mythfilldatabase dropped from 10+
minutes to 2 minutes.  With the --dd-grab-all option, total time was 17.5
minutes.  Before the change it was 1-2 hours if it didn't timeout.  IO wait
times have gone from 20% to 5.5%  when running "iostat 5". My database type
is myisam.

David McMillan
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