[mythtv-users] Backend Hardware Questions

[Dan Wilga]

On 1/16/15 2:14 PM, Henk D. Schoneveld wrote:
> On 16 Jan 2015, at 19:47, Henk D. Schoneveld <belcampo at zonnet.nl> wrote:
>> On 16 Jan 2015, at 19:03, Jan Ceuleers <jan.ceuleers at gmail.com> wrote:
>>
>>> On 16/01/15 11:36, Henk D. Schoneveld wrote:
>>>> I would suggest check power-consumption first with a Kill-Watt device,
>>>> most PSUs are way to big and are most efficient when loaded at > 75% of
>>>> max capacity. HD’s don’t use that much power.
>>> Power supplies need to be dimensioned not for average load but peak
>>> load. Which occurs at boot when the disks all spin up at more or less
>>> the same time.
>>>
>>> So unless you have a fancy controller that spins the disks up one by one
>>> you need a lot of headroom on top of the system's average load after boot.
>> You can watch what booting needs, you’ll probably surprised how low it is. Of course you can also encode multithreaded and see how high it goes.
> MAX TDP of X4 B50 =95W
> Under max. load with 5 - 8 drives it will < 150W
I agree. Much of the specs of power supplies has to do with marketing to 
gamers and folks who automatically assume that a higher-rated power 
supply is better.

In fact, when two power supplies are rated with one of the "80-Plus" 
variants, it's actually possible for a PS with a higher wattage rating 
to consume more than another with a lower rating.

That's because the 80-Plus certification applies to a 20% draw, on the 
low end. So if your system is only drawing 120W with an 800W supply, 
that's 15% and could be less than 80% efficient. A 500W would be 24%, so 
it's supposed to be at least 80% efficient.

I'm currently spinning 8 drives with an ION motherboard. The usual draw 
at the wall is about 130W. A power supply 650W or greater would go under 
the 20% threshold. (I'm using a 500W, IIRC).