[mythtv-users] Power efficient backend-only server

Vitani vitani-mythtv at tfxsoft.com
Wed Oct 21 15:10:48 UTC 2009

> > Good afternoon Greg,
> >
> > Thank-you for your reply, I just have a few questions.
> >
> > - If I'm running Nova-Ts, why would I not be running commercial skipping?
> I
> > am running it on all my recordings, and it appears to work (I don't
> actually
> > use a MythTV frontend, so I have never actually tried skipping the
> adverts),
> > is there something I don't know about the Nova Ts?
> I though Nova-Ts where DVB and Commercial skipping on that did not
> work well (in the UK at least).
> Commercial skipping involves quite a bit of processing power (looking
> at each frame I believe) which is quite a bit of IO/CPU work - which
> is not what you are aiming for.
> If this is important, you might look at the recent posts involving
> stepping down the CPU Speed and getting a CPU that supports that well
> combined with a decent motherboard chipset (ie a low power one).
> But if you are not skipping the adds why bother?  Or have I missed
> something?
Good point, I could quite easily live without it! I've always left it on as
that's the default

> - Assuming I turn commercial detection off, would you agree that anything
> > over 800MHz (the slowest Atom) would be fine for recording & file
> sharing?
> Others might be able to answer is 800Mhz is too low, but I would be
> surprised if it did not work ok.  This assumes your file sharing is a
> little lightweight.  SMB (Samba) sharing lots of large files across
> loads of clients might not work too well!
> There appear to be lost of reports of success with fan-less Atom
> boards - I cannot remember hearing of an issue, but you would need to
> check!
I was thinking of getting the PVR bundle from mini-itx.com (
http://www.mini-itx.com/store/?c=38), but I think I may be better off with
something a little more powerful, as I will be sharing these large video
files to anywhere up to three clients. I'm thinking about getting a Jetway
J7F4 board (http://www.mini-itx.com/store/?c=2#j7f4k) - 1.2GHz should be
enough I think, with 1Gb of RAM.

> > - Do you know if USB tuners draw less power than PCI ones?
> I would assume yes as the USB spec power is actually quite low (5w?)
> and you can get twin tuners, whilst my 2xNova-T's draw about 5w each.
> Not sure what the 500 pulls.
> I may be able to tell you in a few weeks when I work out which dual
> USB tuner with remove IR sensor to get.
> > - Does recording more than one channel at once make much of a difference?
> At
> > the moment I have the two tuners (on a single PCI card) set to record up
> to
> > 3 channels each at the same time (to cover the over lap at the start/end
> of
> > two recordings on the same channel). Theoretically (although it's never
> > happened in practice) at the moment my set up could record six TV
> channels
> > at once.
> It will make a small difference;
> - Nova'ts will probably draw a little more power (minimal)
> - Backend/System has to shut that content off to storage (minimal)
> Call it a watt or 2 at a guess.  It would be worth a test to record 6
> things at once and watch what happens, as here there will be a
> reasonable amount to shift IO wise.
> Assuming 2Gb/hr per recording (av SD on my stuff roughly, YMMY) =
> 12288 Mb an hour = 3.41 Mb/Sec.  You would be starting to approach the
> speed of 100Mbit networking and the network file protocol ie I only
> get slightly more than this on a Samba shares on my SP13000 on a
> 100Mbit wired network.
> So it depends if you really need to be able to record 6 channels at once.
Hmm, I'm tempted to replace my tuner too now, plug it into a USB port
internally (the case I'm thinking of getting has two internal, designed for
WiFi - http://www.mini-itx.com/store/?c=54) and find a hole big enough to
put the areal lead through :)

Thanks again Greg, I shall let you know how I get on!
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