[mythtv-users] Architecture Idea - Raspberry Pi, VM, XBMC

Simon Hobson linux at thehobsons.co.uk
Sat Jan 5 19:53:33 UTC 2013


"Mark Gardner" wrote:
>- DVB-S2 USB tuner on a Raspberry Pi running a MythTV Slave backend
>- DVB-T2 USB tuner on a (second) Raspberry Pi running a MythTV Slave
>backend
>- MythTV Master backend (with no tuners of its own) running in a VM
>- Data storage to be on a NAS
>- XBMC Frodo PVR as MythTV Front End running on dedicated hardware
>
>Both tuners would be dual tuners ideally, but I've not seen any suitable
>yet. 
>
>- Is Pi man enough to run a backend?
>- Is a master backend (no tuners) in a VM a viable option?


Apart from the "my box drinks less juice than your box" subthread ...

Firstly, it used to be the case that a backend with no tuners wasn't a supported configuration - and I've heard nothing to say that's changed.
You can run a backend, with tuners, in a VM - my first Myth backend ran as a Xen guest on a single core AMD64-3200 with 2G RAM total and one disk. Other guests ran my home server and router. It was "far from ideal" and I had to more or less abandon commflagging, but it could manage 2 recordings (multirec off one DVB-T tuner) and 1 playback of UK Freeview SD reasonably well, and could just about manage 3 recordings though by then the bottlenecks were making themselves known.

TBH, by the time you've added all your stuff together - a couple of Pis with their tuners, a VM guest, the NAS, a network switch - I think you'll find that you aren't any better off than running a dedicated low power backend with everything in it. For example, an HP Microserver* can run at around 40-50W with a couple of disks spinning and that's got the "oomph" to run your full backend (though not the CPU horsepower to do real-time transcoding).

I was planning to run my current backend as a VM under Xen on a Microserver, but I couldn't get the tuners to work with Xen loaded and more than 4G RAM in the machine. So I ended up with 2 Microservers.

* Yeah, I know I keep mentioning them, but for a complete low power (and quite quiet) small server box they are pretty good value - especially with the "never seems to end" cashback offers on them. Though a quick check on eBuyer says that the plain cashback has ended, and the current offers are only if you buy it with a Micro$oft OS :(


I too find the current fad for "Pi with everything" a bit odd. Yes, it's a lot for a little money, but it's not the right tool for everything. I see a lot of projects where it's clear it's not the right tool - but I think a lot of people are taking the approach that for the cost saving (vs perhaps some more appropriate small system) they'll live with the downsides. I also feel sorry for the vendors of other small/embedded system who don't have the advantage of what was in effect a lot of free help from Broadcom and thus can't write off all the man hours it took to develop their embedded systems - but are now having their market savaged by the Pi rush.


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