[mythtv-users] Disk Access

Stephen Robertson stephengrobertson at gmail.com
Thu Dec 13 09:10:20 UTC 2007


On Dec 11, 2007 9:53 PM, Douglas Wagner <douglasw0 at gmail.com> wrote:

>
>
> On Dec 11, 2007 3:37 PM, Craig Huff <huffcslists at gmail.com> wrote:
>
> > On Dec 11, 2007 11:37 AM, Stephen Robertson <stephengrobertson at gmail.com>
> > wrote:
> > > I hope you will excuse what is hopefully a very simple question.  I've
> >
> > > noticed an issue with my myth system(1 diskless frontend and 1
> > backend) if I
> > > am recording two dvb programs and watching one already recorded
> > program.
> > > Mostly everything is fine however skipping/fast forwarding/rewinding
> > is
> > > incredibly slow though it usually does resolve itself without falling
> > over..
> > > Backend CPU and memory usage does not seem to show anything untoward
> > and to
> > > be honest I'm not sure how to sensibly measure any disk access
> > parameters.
> > > The disk for the recordings is used solely for storing recordings and
> > is
> > > XFS.
> > >
> > Try executing the command "iostat 4 5".
> >
> > This will report I/O statistics for five samples separated by four
> > seconds each.  The first
> > report will be cumulative statistics since the system was last booted.
> >  The man page will
> > explain what it tells you.  It is easy to have an I/O bound system
> > that doesn't show the
> > CPU burdened significantly, and this sounds like your problem.  Do you
> > have your
> > recordings on a different disk than the O/S and mysql database?
> > Hosting them all on the
> > same disk is frequently a cause of problems.
> >
> > Just to follow up on my original post.  I believe I have tracked down
the cause of my problem and it was just one of those weird coincidences.  I
had inadvertanlty moved my backend machine and this had dislodged one of my
TV cards so my log was filling up incredibly quickly with error messages
which I only discovered when they used up the 2Gb that was free on that
disk.  This just happened to occur at probably the first time I have tried
watching a recording while both tuners were supposed to be in use!

I've since checked the operation (with everything plugged in correctly!!)
and it can quite happily cope with FF/REW through a recording while
simultaneously recording two new shows.

Thanks for your pointers.

Stephen.
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