[mythtv-users] Proposed future power saving networked configuration (0.22 in mind)

[Chris Pinkham]

* On Wed Feb 18, 2009 at 07:37:35PM +1100, Ben Coleman wrote:
> What are the major benefits are a tuner-less master backend? I am curious...

A tuner-less capable master backend means that the master can be a VM
without requiring using USB or network-based tuners on
the master.

I didn't mention that step in my description.  My HDHR is currently
connected to a slave that is a VM on my VMware server.  I'd like to
reverse the situation and make that VM the master and make the current
master a WOL on-demand slave.  Pair that with the fact that I want to
get the HDHR close to the fileserver by putting a slave on my fileserver
just for the HDHR and that means my master would be tuner-less.

> Has anyone calculated how much power you'd actually be saving setting up  
> multiple PC's being started/shutdown every day? ...as compared to  
> powering tuners constantly in a master backend only? I'd be interested  
> in the specs.

You're assuming that people can fit all their tuners into a single
master backend.  You haven't been using Myth long have you? :)  I
personally have  5 PCI-based tuners right now counting the 3 M179 analog
and 2 air2pc ATSC cards.  Putting them all in the master would be one
feat because I'd have to find a motherboard with at least 5 PCI slots,
and that would either have to be new enough to have Gig-E onboard or
have 6 slots so I could install a Gig-E nic.  These numbers are
partially out of the blue, but if my WOL slave uses 35 watts by itself
and 55 with the 2 air2pc cards in it, then it would consume about 500
watts for those 9 hours of recording over a week.  If the same 2 tuner
cards use 20 watts 24x7, that would be 480 watts per day for a total of
2660 per week.  This is assuming 10 watts per card.  Even if you half
that, you'd still be at 1330 per week vs about 400 for the WOL slave.

These numbers aren't as good if you use a power-hungry P4 @ multi-Ghz
that consumes 100+ watts by itself as your WOL slave.  If you don't need
a lot of horsepower and can use a lower-powered older computer or a
newer atom-based motherboard somehow, then the numbers are much better.

> FE for noise considerations, but I can't see how you save power by  
> multiple shutdown/startup sequences. I think people just want a use for  
> lots of small PC's they have stacked in the garage around the house :)

If you wanted to take advantage of wakeup on demand slaves, then you'd have
to see if there was a benefit.  In my case, it means I could turn off
all systems with tuners physically in them (ie, not that HDHR slave on the
fileserver) for at least 1/2 to 2/3 of the day, and with multirec on the
HDHR, some would be off for most of the week (in my case 159 hours Off
compared to only 9 hours On for the whole week).

> I'd hate to have to upgrade everything as well .. I don't think Myth  
> supports a lower or higher version of myth at the frontend than the  
> backend for example which is a shame.

This isn't an issue in my case either.  My MythTV systems are
nfsroot-based, from my msntv2 boxes to my main frontend to my master
backend.  Compile and install once and restart everything and I'm done.
Even if I were using local drives, it's not that hard to run "make
install" or install an rpm on a couple extra systems.

Sure, it will take me years to save enough power to pay for my
programming time to add this feature, but if it's $5-10 less that I'm
paying the power company each month it's worth it now.

One note. I've used WOL in various places in this email, but the
WakeUpCommand is an actual command in my patch, it can be anything to
turn on a system, the same as the current WOLslaveBackendsCommand
setting except mine is for each server specifically instead of a global
command to wakeup all slaves.  I do support the special case of the
WakeUpCommand being just a MAC address.  If this is true, the master
will use builtin code to send a WOL packet so the user doesn't have to
install any more apps to use WOL.  In my case I'll use WOL probably, but
I could just as easily send commands to my Baytech power strip to power
On/Off receptacles to turn slaves On/Off.

--
Chris