[mythtv-users] NFS and remote backend

Patrick Ouellette pat at flying-gecko.net
Mon Jan 14 16:44:03 UTC 2008

On Mon, Jan 14, 2008 at 11:14:27AM -0500, Ryan Steffes wrote:
> The problem, in general, is that the recordings from my OTA HD
> captures stutter slightly during playback, but only while they are
> being recorded.  As soon as the recordings finish, I can watch them
> without trouble.  I'd say this was a network issue, but I can watch a
> /different/ HD recording just fine, just not the one that's currently
> being written to.    The problem grew this weekend, when I reorganized
> my network.    I had been running two combo frontend/backends, and my
> master backend was crammed a little full and got pretty loud and warm
> during recordings.  This weekend, I stuck the recording drives
> (including the DB) and PVR150s into a spare computer and made that the
> master backend and dumped the LVM in favor of multiple storage groups
> to allow the backend to try to optimize disk usage itself.  After I
> got the computers back up and running, I noticed the same stuttering
> problems even on regular streams from 150s.  I changed the option in
> the frontend to "Always stream from backend" (I'm sorry, I can't
> remember the exact option) and the stuttering went away completely on
> low res streams during recordings, but I didn't get a chance to test a
> HD stream during recordings.
> That leads me back to believing it's again a NFS problem of some sort,
> but I don't know what could be causing it.
> Network topology is basically:
> bedroom computer (HD capture card)  -------  1000 link ------   Master
> MythTV   (2x PVR150, Recording partiotions on hda/hdb/sda) ----- 100
> mbs link -----   familyroom computer (Front end only now)
> Bedroom records to mythtv, mythtv records to mythtv, frontend and
> bedroom both playback from mythtv.
> Mounting options are the generic ones recommended in the optimize
> portion of the wiki.
> defaults,bg,actimeo=0,rsize=8192,wsize=8192,nfsvers=3,tcp,soft,intr
> for the 100mbs link, same thing with 32k sizes for the 1gbs link.
> hdparm timings on the drives seem fine (~400 MB/sec cached, ~70 MB/sec
> buffered on all three)
> The fact that it seems like the backend can seemingly stream the video
> with plenty of network space and yet the front end doesn't seem to
> want to read it from the NFS section is what confuses me, and makes me
> wonder if samba could fix the problem.

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?


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"

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