[mythtv-users] Power efficient backend-only server

[Greg Cope]

2009/10/20 Vitani <vitani-mythtv at tfxsoft.com>:
> 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?

> - 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!

> - 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.

> Many thanks for your very detailed help with this! It's just what I was
> looking for.

NP

Greg