[mythtv-users] mythbackend causing server to show significant load at time (resolved)

[Hika van den Hoven]

Hoi John,

Sunday, November 23, 2014, 1:53:29 AM, you wrote:

> Sounds to me like possible HD access overload!


> Tot mails,
>     Hika

> ***********************************************************************************

> So you mean HD as in hard drive I assume.  I have the database on a separate spindle
> than the recordings. I am using two backends and on my main backend I have two
> storage directories on separate spindles but I wonder if it is actually splitting
> my recordings between the different storage directories.  Do you have any hints on
> how I can verify that the problem is an hd access issue?


> ***********************************************************************************

> I wanted to update how I got this resolved.  I tried to un-fragment the video files,
> tried to modify the file system mount options and a few other things and nothing
> really worked.  Then someone mentioned overloading the sata bus.  I only have a four
> port sata on my motherboard and all are being used with, OS Hard Drive, two seperate
> video HD's and a sata dvd player.  Because of this I purchased a pci sata card with
> two ports. I took my one recording Hard Drive off of the on board SATA and moved it
> to the new pci card and now my pixelated recordings have stopped.  I do not know if
> it is just a bad port or too much traffic on the on board sata but either way it is
> resolved. Oh and this also resolved the significant load on the main backend.
> Everything points to this being a getting data off of the hard drive error free
> problem.

> _______________________________________________

Great! It was mainly the combination of those at first glance
unrelated problems that made me think that direction.
The bus load is often forgotten, but you can do the math looking at
the bus bandwidth and the maximum throughput of the individual disks.
I think in general if you have more than incidental disk access you
shouldn't have more than 2 or max 3 drives on one bus. It also helps
if you have disk caching bringing multiple small accesses together in
one big one. That's mainly where DB tuning steps in.


Tot mails,
  Hika                            mailto:hikavdh at gmail.com

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