[mythtv-users] Power Saving Frontend Ideas

Roger Heflin rogerheflin at gmail.com
Sun Apr 13 23:55:56 UTC 2008

Rick Hudson wrote:

>  > plus puts more stress on the components.
> This one sounds like the filament lamp myth! Those always die on startup 
> because it's the most stressful time for them but they do so after their life 
> expectency regardless of how many times they have been started in the interim. 
> Electronics components have a specified mean /time/ before failure (MTBF) and 
> the number of current surges is not a factor provided they operate within 
> their spec.

Hard disk will burn out if you turn them on/off often enough.    MTBF is a 
fictional number that really means nothing, it is calculated usually based on 
rated mtbf of the underlying components, and this rating is based on an 
assumption of how many startup surges that there are, but the calculation is not 
really worth much since the operational data disagrees massively with the 
calculated value, note that on hard disks the official MTBF provided by the 
various manufactures is as least 10x the MTBF calculated from actual failure 
rates, which means that their MTBF is not worth much.  Read Google's report on 
hard disk failures, and I had experience with running ~2000 hard disks for about 
2-3 years, and saw very similar things to what Google's reports has.

And the same is somewhat true of power supplies, the initial in-rush does put 
more wear on the power supply that running, usually the power supplies do blow 
on start up (if they are going to blow).

And I completely agree with the claim of it taking more power to startup than 
run for a long time as being total crap, at worst as your say it might take a 
few seconds  to use the same amount of power as startup on almost anything 
normal people care about.

On a separate note:

On my backend I put in a 80plus power supply that changed the power usage from:
	135W idle -> 120 W idle (-15 W)
	190W heavy cpu -> 165 W heavy cpu (-25 W)

This is for a backend with 5 hard disks in it, and I run recording on it all 
sorts of times and have a number of transcoding jobs on it, so it is not unused 
that much.   My primary frontend is a MediaMVP box (SD only) that uses a trival 
amount of power (<15 watts).

So a decent amount of savings from just a simple change.   Given my power cost 
of <$.06/kwh the 80plus thing does not pay for itself, but for someone paying 
the higher rates it would easily pay for itself.



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