[mythtv-users] recommendations?: energy efficient FE/BE system

[Dave MythTV]

On Sat, Feb 21, 2015 at 5:16 AM, Roger Heflin <rogerheflin at gmail.com> wrote:

>
> On Fri, Feb 20, 2015 at 12:53 PM, Hika van den Hoven <hikavdh at gmail.com>
> wrote:
> > Hoi James,
> >
> > Friday, February 20, 2015, 7:32:27 PM, you wrote:
> >
> >> On Fri, 20 Feb 2015, Hika van den Hoven wrote:
> >
> >>> I don't know how powerful those devices are, but I do all my
> >>> transcoding on my normal (6 core athlon) desktop machine even though
> >>> my backend (dual core) could probably do it too. I can with no problem
> >>> do 4 transcodings at the same time and stil work uninterrupted.
> >>> Just have a slave backend running on the machine you want to use for
> >>> transcoding and disable transcoding on the master.
> >
> >> Thanks for your reply, Hika. It sounds like you're describing a scenario
> >> where the front and back ends are separated, right? If so, I'd like to
> >> keep the combination FE/BE set-up I have, which is why I was asking
> about
> >> whether the ECS hardware would be up to the task of rescaling while
> >> simultaneously recording. It seems possible it might be, since the ECS
> >> system Dave described was said to be a combination FE/BE, like mine.
> Just
> >> was hoping to get a clarification from him (or someone else) on that
> >> before looking further into this option.
> >> _______________________________________________
> >
> > Yes, mine are separated, but also when combined you can delegate tasks
> > to a slave backend, on a computer that you normally use for other
> > things. That's the nice thing of how mythtv is set up and the fact
> > that all your computers are linked through the network. You could have
> > six backends and only one frontend on one of those backends or only
> > one combined one etc., etc.
> >
> >
> > Tot mails,
> >   Hika                            mailto:hikavdh at gmail.com
>
> I have an FM2 processor and the AM1's appear to have similar video hw.
>      My fm2 does appear to do most of the hard work in the GPU.      I
> have an old nvidia ion, an ecs liva, and a fm2 combined FE/BE.     The
> FM2 is nice as the full sized board has 8 AMD supplied sata ports that
> appear to work flawlessly.     With a high grade green power supply
> mine does not appear to be that power hungry.   And the cpus are
> powerful enough that I can also transcode things to codec's that use
> considerably space.
>
>
>

Yep, when you go for REALLY-low-power systems, things get... interesting.
:-)   Trickier to set up, but rewarding when finished.


Before I made my LIVA a BE+FE combo, I was running it as a frontend only,
to a backend machine which had an Intel Celeron 1037U processor (my
previous FE+BE machine).   The 1037U has about twice the performance of the
N2807 in benchmarks, and with a 17W TDP, was quite low power as well.
Nowhere close to the 4.3W N2807, but still just a fraction of the desktop
class machine it replaced.

However, when I took apart the 1037U machine and transferred the database,
tuners, and hard drive over to the LIVA and brought it back up as a FE+BE
combo, it was noticeably more responsive and pleasant to use than the two
separate systems... even though those two together had THREE TIMES the
processing power of the LIVA on its own.   The network transferring was the
weak link.   So adding a machine and splitting functions doesn't "always"
make things better.  :-)

On my LIVA, I did encounter problems when doing multiple recordings while
commercial flag jobs were running.  Restricting the commercial flagging to
run in an overnight non-prime time slot easily solved that, and so far for
my usage, it hasn't ever had a problem getting through them.  A worthwhile
tradeoff for me.


Another example:  On the 1037U system, I did some experimenting with using
a Broadcom "Crystal HD" mini PCIe card for the heavy lifting of the video
decoding.  It turned out that while it worked (70%+ reduction in CPU usage
and clocking down from the decode offload), the overall power consumption
for the system had actually risen slightly when playing video content.
So... saving power that way didn't quite work, even though on paper it
looked like a good idea.


It's also worth noting that there are diminishing returns.   Like I
mentioned earlier, with the LIVA, it's so low power that your storage
drive(s) will likely consume more power than your computing box.   So you
start looking elsewhere...   I spent $27 and dropped another 5 watts of
"always on" power usage by upgrading my old wireless router... something no
amount of optimization would be able to do anymore with my always-on MythTV
box.


Deciding what to have sleep and what to have wake up is another challenge.
Some do scripted shutdown/wakeup on FE/BE boxes, others leave them running
to be available for other purposes (AirPlay target, UPnP media server,
etc.).  Some have an always-on backend but use a sleep/wake-on-demand
frontend.  Some feel like 65 watts at idle isn't worth it to bother
shutting down, some cringe at the thought of 65 watts at LOAD, and some
feel like 150+ watts at load is OK because it's shut down when not in
use.   Some live off the grid, and some live in cold climates with cheap
electricity and use their MythTV machines as space heaters.  Everyone has a
different opinion and different priorities.   :-)

- Dave
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