[email protected] wrote:
> Device:         rrqm/s   wrqm/s   r/s   w/s    rMB/s    wMB/s
> avgrq-sz avgqu-sz   await  svctm  %util
> sda               0.41    13.61  2.17  5.93     0.03     0.08
> 26.28     0.29   35.16   1.25   1.01
> sdb               0.02     0.00  0.00  0.00     0.00     0.00
> 20.44     0.00    3.47   2.48   0.00
> sdc               0.16     0.05  1.99  1.56     0.19     0.10
> 167.25     0.04   12.46   7.05   2.50
>
>>What purpose do these two drives serve in your system?
>
> sda - core OS drive, repository for backups from other systems that
> run at 2 am (and otherwise don't touch it), zomeminder database
> sdb - old myth drive, still ext3 from previous experiments
> sdc - new (current) mythtv drive, which is used for nothing but
> mythtv as it's data store.

You mention a zoneminder database on sda, by which I presume you mean the
place the images are stored for events. That device seems to have high
write requests at the time (wrqm/s). I presume your mysql database is also
on this disk, both for zoneminder and mythtv.

This would lead to potentially high contention for random access to that
drive when zoneminder is capturing events, as it is writing images to disk
and adding data to mysql at the same time that mythtv is heavily accessing
the mysql database for the seektable.

Have you looked for a correlation between stuttering and zoneminder
capturing events?
-- 
Mike Holden

http://www.by-ang.com - the place to shop for all manner of hand crafted
items, including Jewellery, Greetings Cards and Gifts



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