[mythtvnz] NFS performance not good enough?

[Jean-Yves Avenard]

On 5 June 2014 17:15, Worik Stanton <worik.stanton at gmail.com> wrote:
> I have a problem with my recordings not finishing.  On examining the
> logs I see that it is due to disk performance.  I am writing to a disk
> over NFS.  It should be able to take it, I thought, and these problems
> have only started recently.
>
> (See below for my logs and why I thing this is the problem)
>
> So I have 2 questions for this list:
>
> (1) Should I expect NFS to manage?  Searching the internet does not turn
> up many other people having problems.  I have got file caching turned on
> (using the 'fsc' option and cachefilesd.  (I'm turning that off now to
> see if it helps)

I write over NFS to a FreeNAS ZFS array without issues.

What I did find however, is that all the fancy NFS tutorial on how to
increase performance are all wrong, and in fact compromise speed
enormously.
Leave the read/write buffer as they are calculated by the system,
don't play with it.

I mount the NFS share using the following option:
192.168.200.13:/mnt/pool/data/videos/recordings /external/recordings
nfs proto=tcp,timeo=14,noatime,actimeo=1 0 0

that is it.. e.g. leave it to the system to calculate buffers, and
don't update the creation and last modification time

I use gigabit jumbo frame on the dedicated link between my myth
backend and the NFS server, but it actually makes little difference in
my experience

I do over 100MB/s writing to the server, which it more than enough to
record a dozen HD stream simultaneously

>
> Jun  4 22:51:33 gently mythbackend[1425]: E DVBRead
> ThreadedFileWriter.cpp:216 (Write)
> TFW(/media/Recordings/1010_20140604222900.mpg:62): Maximum buffer size
> exceeded.#012#011#011#011file will be truncated, no further writing will
> be done.#012#011#011#011This generally indicates your disk performance
> #012#011#011#011is insufficient to deal with the number of on-going
> #012#011#011#011recordings, or you have a disk failure.
> Jun  4 22:51:40 gently mythbackend[1425]: W TFWWrite
> ThreadedFileWriter.cpp:499 (DiskLoop)
> TFW(/media/Recordings/1010_20140604222900.mpg:62): write(58092) cnt 2308
> total 134209816 -- took a long time, 16819 ms
>
make sure you are running the latest fixes/0.27 build, several
improvements were made in this area.

but yes, it does appear your disk is too slow