[mythtv-users] S-L-O-W DB ops

[networks1 at cox.net]

---- MythTV <mythtv at blandford.net> wrote: 

=============
On 11/11/2011 04:18 PM, networks1 at cox.net wrote:
> Greetings. I've just gotten finished with migrating mythtv to a new setup (FC12 ->  FC15).  I restored the db from the old setup, but now both setup and mythfilldatabase are running really slow.  It takes like an hour for mythfilldatabase to run, and there's a long pause after it says ...written to STDOUT at which time the disk runs straight time.
>
> I searched around and found a thread by someone else with this problem, and people were speculating that it had something to do with the EXT4 settings, but the thing is AFAIK I'm running the same (default) settings as on the old setup with partitions and sizes as recommended in the wiki, which  ran fine.  I've applied the suggested settings to /etc/my.cnf, viz
>

I had this problem with FC15 as well.  It turned out to be related to 
the kernel enabling barriers by default.

Disabling barriers made my mythtfilldatabase performance go back to the 
way it was previously.

Add 'nobarrier' to your fstab for the partition that contains your mysqldb.

Michael

=============================

Thanks for the input.  So I had a look at the entry in fstab and right now it's "defaults."  Did you change to defaults,nobarrier or just replace it with nobarrier?

I also found https://wiki.archlinux.org/index.php/Ext4 which says "Users can improve performance with the nobarrier option when mounting the disk, but this can be dangerous [2] and may result in data loss or corruption after power failures. To turn barriers off, add the option barrier=0 to the desired filesystem"

So I presume that's the right thing to do, but again append it after defaults, or replace?

Steve