[mythtv-users] NFS and remote backend

Ryan Steffes rbsteffes at gmail.com
Mon Jan 14 16:14:27 UTC 2008

On Jan 13, 2008 6:09 PM, Michael Heironimus <mkh01 at earthlink.net> wrote:
> On Sun, Jan 13, 2008 at 03:07:23PM +0000, Stroller wrote:
> >
> > On 12 Jan 2008, at 14:25, Michael Heironimus wrote:
> >
> > > On Sat, Jan 12, 2008 at 01:39:29PM +0000, Stroller wrote:
> > >>
> > >> On 11 Jan 2008, at 18:08, Yeechang Lee wrote:
> > >>> ...
> > >>> As I've commented here several times over the past two+ years I've
> > >>> been running MythTV, CIFS works great for transfers of the large,
> > >>> multi-gigabyte files MythTV uses, while NFS's performance is abysmal
> > >>> by comparison.
> > >>
> > >> Quick question - I'm sure I could Google it, but I'm pretty sure
> > >> you'll be able to tell me off the top-of-your-head - how do you
> > >> ensure CIFS is used, instead of Samba, please?
> > >
> > > CIFS is just a protocol. Samba is an application suite that implements
> > > that protocol. Linux smbfs (old) and cifs (new) mounts implement the
> > > client side of the protocol.
> >
> > My apologies - you're of course perfectly correct.
> >
> > Let me rephrase my question:
> >
> >     How does ensure that Samba uses CIFS instead smbfs, please?
> Specify the filesystem type as cifs instead of smb on the client. cifs
> and smbfs have slightly different mount options, so check your man pages
> if you're switching.

I haven't had time to test this thoroughly, so I hadn't posted asking
about it yet, but I've just reorganized my network mostly to reduce
heat and noise, but I had hoped it would fix a stuttering problem
during playback of HD recordings, particularly while they are being
recorded.  I noticed this thread, so I though I'd go ahead and post.

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.

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.



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