[mythtv-users] nfs pauses

Dale Pontius DEPontius at edgehp.net
Tue Nov 10 23:22:54 UTC 2009

Yianni Vidalis wrote:
> Hi.
> I am facing a strange problem lately and I hope someone here can provide
> some insight (or a solution....).
> Most of my videos are stored in an nfs share. The share is mounted in
> fstab using rw,rsize=32768,wsize=32768,bg. While watching them on my
> frontend, there are occasionally pauses, as if the file "is not there"
> when the frontend needs it. I notice it especially with films with AC3
> sound because the "AC3" led on the amplifier is turned off momentarily.
> The nfs share is on an opensuse 11.1 pc, stored on raid 5 on top of lvm
> (talking about redundancy....). The strange thing is that I didn't
> always have this problem, it must have happened after one of the latest
> package upgrades, so I suspect something to do with the latest opensuse
> kernel ( x86_64). The ethernet card is an onboard gigabit,
> using the r8169 module. The frontend card is 100mbps (8139too module).
> I am running mythtv trunk, version 22772. I thought it might have been
> VDPAU, but disabling it made no difference. I am using Graphite, so
> turning off "Extra audio buffering" would not make any difference. I
> also tried with actimeo=0 and 5 and with the option completely removed.
> Same behaviour.
> Using the system monitor on the nfs server, I noticed that that network
> throughoutput is non constant, but the videos are served in "peaks"
> around 20 secs apart. The pauses occur during these peaks, which are
> shorter and wider when a pause occurs.
> Watching part of a suspect video with xine was smooth, although I admit
> I watched only 5-6 minutes of it. Moving the file locally and watching
> it in mythtv shows no problems, either.
> I have no other network problems between the two pcs, the ssh
> connections are never broken even after hours of idle time, file
> transfers are smooth and fast for 100mbps network. Is it true to suspect
> that some latency has increased, either on the filesystem or the network
> driver? Has anyone faced any similar problems? Can you please suggest a
> possible solution?
> Thank you for a very great program, I am very happy that 0.22 is out,
> although I will continue to run trunk because now I'm ... addicted to it.
> Thank you,
> Yianni.

There are 2 possibilities I can suggest.

First, there were some NFS problems in the kernel, starting around
2.6.25/26 and finally getting fixed at 2.6.29.  If you're comfortable,
you might want to manually upgrade your kernel.  2.6.29 is reasonably
compatible with 2.6.25/26 - it's 2.6.30 where things started moving kind
of fast and required significant configuration tweaking.

Second, are you by chance also running your $HOME directories on the
same NFS server?  When Firefox moved to sqlite for storing its stuff, it
became rather infamous for filesystem stress - and that's stressing
local filesystems.  I was running this way, and it was bringing my NFS
server to its knees periodically.  I've since symlinked $HOME/.mozilla
back onto a local filesystem and things have gotten better.  None of
this was helped by the fact that my servers are ancient flea-market or
hamfest junk, and perhaps easily overwhelmed by a modern system.


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