[mythtv-users] NFS and remote backend

Jason spuppet at comcast.net
Mon Jan 14 16:38:19 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.


> 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.
> Thoughts?
> Ry

I've seen the same situation here in my setup.  I had everything exported 
from my master backend via NFS (same mount options you came up with) to the 
frontend.  The frontend was only that, it was not a slave backend.

I was seeing a lot of stuttering with NFS being the source for video files, 
with the worst showing in shows being recorded.  I switched to streaming 
direct from the backend and most of the stuttering went away.

The only place I see stuttering is when I'm watching something already being 
recorded, or watching live TV.  The stuttering only seems to occur when I'm 
watching close to the end of the recording (i.e. almost at real time).  If I 
pause for about 10 seconds, the stuttering goes away.  On the frontend, I 
see lots of the "prebuffering pause" messages during this stuttering, which 
is expected.  I do see prebuffer issues at other times, but I don't recall 
noting an actual stutter in the playback.  If there is, it's quite small and 
mostly unnoticeable.

I've got gigabit network between the backend and frontend.  My HD recordings 
come from a HDHomeRun.  I have not implemented jumbo packets on the gigabit 
network.  For network performance purposes, I'm looking to implement 
ethernet bonding for the backend (I've got two gigabit ports on the 
motherboard) and possibly vlans to segregate gigabit with jumbo packets from 
the rest of the network.  (I don't think those changes would really help 
anything other than my own sense of "it's running best it can".)

I installed a DCH3200 set top box from comcast over the weekend, connected 
via firewire, and noticed the same stuttering issue with that source. 
Again, pausing helped the problem.

One item of note:  I can record two HD streams from the HDHR and watch a 
previously recorded HD program without any stuttering, so it appears that 
all the hardware can "keep up" with the requirements.  Something just breaks 
down when I'm watching something being recorded that is close to the end of 
the file.

Given that I'm seeing the stuttering without NFS, I'm not sure it's the 
source of the problems.  Nor would I imagine moving to Samba/CIFS would 
help.  Maybe it's some sort of file system problem on the backend (locking, 
etc?).  I'm using ext3 on the media partition.

Aside from doing the work to figure out that streaming from the backend 
helped, I haven't done much to suss out the reason for this.  I accepted the 
situation it was in and the relevant requirement to hit pause at the start 
of live tv.


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