[mythtv-users] Moving MythTV backend to another computer

Wed Apr 2 17:33:07 UTC 2014

On 2 April 2014 at 15:17:57, Michael T. Dean (mtdean at thirdcontact.com) wrote:
> On 04/02/2014 09:42 AM, Sam Jacobs wrote:
> > On 2 April 2014 at 14:23:22, Michael T. Dean wrote:
> >> You still need a master backend somewhere on the network. This is just
> >> for the "extra" computers that do things for MythTV but don't have
> >> tuners. They needn't be remote backends (and all the tons of extra
> >> resources running one requires -
> >> http://www.gossamer-threads.com/lists/mythtv/users/365270#365270 ),
> >> especially since running a backend without tuners breaks some parts of
> >> MythTV.
> > Yeah, but the tunerless machine is the only reasonable candidate for the master backend  
> role.
>  
> The only way that could be true is if it's because you are trying to
> avoid running cables. 

I’d ask my fiancé whether he thinks I’m trying to avoid running cables, but I rather think that his answer would be unprintable!

> Running 2 backends is actually a waste if you
> don't need them, and I can't think of any reason you'd need more than
> one backend except for scalability reasons--i.e. you have more tuners
> than you can fit/power/... in one backend. And, anywhere you have a
> backend, you have to have network cables, so in many cases you can use
> network tuners and use the cables you have already run.

Mac OS X doesn’t have drivers for USB tuners, not any that MythTV can talk to, anyway. I did try using a Linux virtual machine, but neither Parallels nor VirtualBox would work. If I could use my tuners on the Mac mini then I wouldn’t be running a slave BE. Having it all in one—very, very quiet—machine would no doubt boost “W”AF, but there’s no way to do that, presently.

> From a power perspective, the remote backend wastes all the power it
> uses when it's on--compared to having the tuners in the always-on PC.
> Even if an idle tuner is using more than negligible power, the
> likelihood that its times 24 hours per
> day is greater than the watts times
> is very small (unless you barely ever run
> it/record TV).

Oh certainly, *if* I could have just one box running at any given time then it would please His Nibs the Lord TurnEverythingOffAtTheWall no end, but this is an Apple household, and the mini is our always on machine, since before I started using MythTV again. It serves all our media, provides Back to My Mac access, my MacBook backs up to it, we rip Blu-rays with it, etc.

Plus the PC that I’m using, while a whole lot quieter that the one I was using before it, isn’t nearly as quiet as the Mac mini.

> From a robustness perspective, it adds additional potential points of
> failure--from failing to wakeup to network failures preventing
> communications with the master backend/mysql server to ...

I do worry about that, but in the last 3 months or so I’ve only had that sort of problem once, and that was mythbackend crashing on the slave, which could just as easily have happened, and would’ve affected me the same way, if it was the sole backend.

In fact, having the machine with the tuners in it *not* on 24/7 improves robustness, because the Linux drivers for my tuners are none too stable. It can be up only about 48 hours before I start getting 0 byte recordings, then I have to reboot it.

> So why can't you have your master backend have tuners and be the
> always-on PC?

See above.

> > Otherwise I’d need to have the PC on simply to schedule a recording, or edit a rule! Or  
> does mythmediaserver also run the scheduler?
> >
> > I’d really appreciate it if you could point me to something I can use to educate myself  
> as to the specific reasons *why* I shouldn’t have my MythTV system set up the way that I  
> currently do. It doesn’t give me any problems currently, but I’m not using all the features  
> of MythTV and if this setup is going to cause me pain in the future, I’d like to know how.  
> >
>  
> No, as of now, the master backend does all the scheduling and such. It
> must be a backend. This is why I recommended just making the always-on
> PC the master backend and sticking tuners in it (or using network tuners
> or ...) or, alternatively, making the master backend system the
> always-on PC. (So, you could either stick tuners in the current
> always-on PC and run cables for the tuners to it, or you could move the
> current always-on PC to the location with the TV inputs and stick tuners
> in it, or you could move the processes/services that the always-on PC
> provides to the system that's near your TV inputs and make that the
> master backend.)

Unfortunately it’s not always that simple.

> In the future, we may split the scheduler from the recorders (we will if
> I can convince the others and make the time to finish it).

I truly hope you manage to do that. My Mac mini only has 4 GB of memory, so anything that could reduce the load would be very welcome.

> Until then,
> the scheduling is in mythbackend, and we don't support running a
> "scheduling-only" backend without tuners--so if doing so, problems you
> encounter may well be related to your running in an
> unsupported/untested/known-to-have-some-problems configuration.

What problems is this configuration known, or suspected, to have/cause?

Thanks,
Sam

> Mike
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--  
Sam Jacobs on MythTV 0.27, UK Freeview SD & Freesat HD, EIT-only EPG
Mac mini, MBE+FE: OS X Mavericks, bundled FE, macports BE
Acer Aspire L310, SBE: Debian testing, Elgato EyeTV for DTT Stick (Hauppauge Nova-T USB Stick in disguise!) & DVBSky S960 DVB-S2 USB

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