[mythtv-users] Performance, TV, Network, Video Cards, Identifying bottlenecks (long)

[Mike Benoit]

On Sun, 2003-04-13 at 13:39, Eni Gma wrote:

> 2.  Network Performance.  As I stated above, I am attempting to use a 
> remote NFS server for storing recordings.  When I am trying to record 
> something and watch it on frontend 2 (which can watch live TV with 
> almost acceptable performance) the video stutters as described above.  I 
> am wondering if these problems are related to network performace.  The 
> NFS server and the backend server are connected via a 24 port netgear 
> 100 Mb rackmount hub.  During the testing phase the frontends have been 
> connected to a 8 port 100 Mb D-link switch.  Is it possible that my 
> problems viewing programs that are recording are related to network 
> performance?  What are the bandwidth requirements for recording (and 
> playing back) programs?  Are there other people who are using NFS mounts 
> to record programs?  With so many variables (backend performance, 
> frontend performance, network performance, file server performance, 
> etc.) it is hard to narrow down where the problems are.  Is it possible 
> that I need to upgrade to a switched network for the backend servers (or 
> even gigabit??).  Or are my problems related to system performance and 
> not network performance?
> 

As I write this I have a XP2400 (o/c'd to 2135Mhz) recording and
watching Live TV at the same time, with the Live TV ring buffer, and the
video dir all mounted over NFS (no local IO). Its pushing about
1.2megabytes/sec over 100mbit D-Link hub. Of course it all depends on
how well your NFS is tuned, and more importantly what video format your
using. Obviously RTJPEG will probably use much more bandwidth. I'm
currently using 512x384 (didn't seem to notice the difference between
this and 640x480) MPEG4 with a bitrate of 3000, min quality: 1 max: 5
diff: 3.

Try benchmarking your NFS setup:

time dd if=/dev/zero of=/mnt/video/test.out bs=16k count=16384

I can easily push 10megabytes/sec with this test.

-- 
Mike Benoit <ipso at snappymail.ca>