[mythtv-users] backends without tuners (was Re: Transcoding is being done on frontends, not backend)

[Craig Sanders]

On Thu, Jan 08, 2009 at 01:57:17PM -0800, Brad DerManouelian wrote:
> > "Remove" meaning don't run it--don't uninstall it.
> 
> Curious as to why you recommend leaving the backend installed on a  
> frontend machine. If there are no tuners on the machine, it's not good  
> and even potentially harmful to run.

since when is it harmful?

i have BE installed on all my FE boxes (mostly amd64 workstations with
myth installed so we can watch TV & videos at our desk if we want) just
to make use of additional CPU power while transcoding multiple shows at
once. it works fine. i start the transcoding jobs manually after editing
out the ads...sometimes there are 8 or more transcoding jobs running at
once.

in fact, myth's network-centric model was the main reason i switched
from running VDR to myth last year....was waiting for multirec. since
then, i've gone from VDR w/ one tuner card on one machine (plus an xbox
running xbmc) to myth w/ 5 tuner cards on 4 machines (with the xbox
retired).


here's my current setup:

ganesh  - master BE - amd64 x2 5200 8GB RAM, 1 Nova-T 500 dual tuner
          & FE        also my file, web, dns, mail, mysql, postgres, 
                      and everything else server. and my main
                      workstation. nvidia 7300GS

indra   - BE & FE   - amd64 x2 5200 2GB RAM, 3 DVB-T cards, connected
                      to panasonic TX47P800H rear-proj TV. dedicated
                      TV-watching front-end.  1 x dvico fusion lite, 1
                      x twinhan vision plus, 1 x hauppage wintv 9002.
                      nvidia 8400GS.

(indra has 4GB extra RAM waiting to be installed, but the old DVB cards
don't work if there is more than 3GB installed. haven't been able to
confirm it yet, but my guess is that it's the twinhan (bt878) causing
the problem. the dvico fusion lite (also bt878) used to work fine in
ganesh with 4GB installed, and the hauppage is a newer cx88 based card)

kali    - BE & FE   - amd64 x2 5200 6GB RAM, no tuners.  my partner's
                      workstation.  nvidia 8400GS

durga   - BE & FE   - AMD64 3200, 2GB RAM, no tuners, connected to 
                      TEAC TV in back room. also spare w/s for guests
                      & visitors. mostly working, but still a work in
                      progress.  I may add another tuner card here or
                      maybe not. and i still need to set it up for dual
                      screen (TV and a 22" LCD monitor). nvidia FX 6200
                      (AGP).

durga is only turned on when needed. the others are on 24/7. all
are running amd64 debian 'sid', with the latest myth packages from
debian-multimedia (0.21.svn20090101-0.0).

both indra and ganesh export their myth directories via nfs4. this
mostly works, but there are annoying problems when both machines need to
be rebooted (they are each dependant on the other for NFS mounts. not
good)

in total, there are 5 DVB-T tuners on 2 machines. each machine is
configured to allow 2 concurrent jobs per CPU core. durga was only built
last week, and i only started running the BE on kali after that.

on some nights, there are 6 or 7 programs being recorded simultaneously
(i tend to record a lot of stuff i either never get around to watching
or watch weeks later). before kali & durga, that meant there weren't
enough CPUs/jobs to do the commflagging while recording if there were
any transcode jobs running too. now there is.



i'm in the middle of re-organising things here.  I plan on getting two
more dual-tuner cards (probably dvico dd4 or nova-t 500s) and getting
rid of the old DVB cards and having all three dual tuners in indra, so
it will be the only machine with tuner cards. indra currently has 2
x 300GB drives in it, but (after moving ganesh from 4 x 500GB drives
onto 2 x 1TB drives yesterday) i have 4 x 500GB WD drives ready to be
installed into indra. i'll probably do that today sometime....next
scheduled recording is in 8 hours so that's plenty of time :)

when that's done, i'll make indra the master BE and have all the other
machines be FEs and secondary BEs.

and i'll replace my current 100baseT switch with a gigabit switch. the
cabling is all cat-5e so should be fine for gb.

craig

-- 
craig sanders <cas at taz.net.au>

Computers are useless.  They can only give you answers.
		-- Pablo Picasso