[mythtv-users] NFS and remote backend

[Patrick Ouellette]

On Mon, Jan 14, 2008 at 08:38:19AM -0800, Jason wrote:
> 
> 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.
> 

Could this be a case of MySql not keeping up?  Database writes slowing
down the availability of the inprogress recording?

Pat
-- 

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"