[mythtv-users] NFS and remote backend

[Patrick Ouellette]

On Mon, Jan 14, 2008 at 02:37:38PM -0500, Ryan Steffes wrote:
> Date: Mon, 14 Jan 2008 14:37:38 -0500
> From: Ryan Steffes <rbsteffes at gmail.com>
> Subject: Re: [mythtv-users] NFS and remote backend
> To: Discussion about mythtv <mythtv-users at mythtv.org>
> 
> On Jan 14, 2008 1:20 PM, Patrick Ouellette <pat at flying-gecko.net> wrote:
> > On Mon, Jan 14, 2008 at 01:05:15PM -0500, Patrick Ouellette wrote:
> > > >
> > > > >
> > > > > Are you running two NICs in the master box (one on the gigabit lan and
> > > > > one on the 100 mega bit lan) or are you relying on a combination switch
> > > > > (10/100/1000) to handle the different bit rate conversion?
> > > > >
> > > > > Pat
> > > > > --
> > > >
> > > > I'm running through a D-Link firewall/router to handle it.
> > >
> > > So you are expecting an NFS client set for 8K blocks to work well on a
> > > network with a server and another client set at 32K blocks.  I wonder if
> > > that has anything to do with it.
> > >
> > I reading that on the list, it sounds a bit harsh.  Not meant to be an
> > attack, more thinking out loud.
> >
> > The other thought that comes to mind is are you optimizing your
> > database?  A clean database is a happy database.
> >
> >
> 
> I would only expect that to be a problem if network latency was
> suffering across the board, but it isn't.  If I was getting bad
> network timings in general, I'd think adjusting that might fix it, but
> the problem seems to be exclusively to reading the files off the NFS
> share.  I run the optimize script on the DB regularly, but I haven't
> gone into tweaking mysql parameters.  Based on what other people do, I
> wouldn't think that /should/ be necessary.  I'd be a lot happier
> blaming network settings if it failed both ways, instead it seems to
> be something about the nature of the NFS that's failing.
> 

The other programs using the network may be more forgiving of timing
issues.  The display of video without stuttering requires the information
for the video frame to get to the frontend with enough time to be decoded 
and rendered. If the frontend is waiting on data from the network it
will stutter.

You can try the following to see if anything stands out as odd:

Run some NFS tests with large file reads and writes on the NFS share
from the 100 mega-bit frontend.

Change your NFS block size on the client & server (restart NFS) and run
the tests again.  (large file means many times greater than the 32K
block size)

Repeat the above tests with a crossover ether net cable connecting your
server and client (at 100 mega-bit). This eliminates the D-Link
router/switch.

Install SAMBA, and run the tests again using the CIFS share from SAMBA.


Pat

-- 

Patrick Ouellette                 pat at flying-gecko.net
kb8pym at arrl.net                   Amateur Radio: KB8PYM 
Living life to a Jimmy Buffett soundtrack
"Crank the amp to 11, this needs more cowbell - and a llama wouldn't hurt either"