[mythtv-users] Backend Hardware Questions

[Henk D. Schoneveld]

On 16 Jan 2015, at 20:59, Dan Wilga <mythtv-users2 at dwilga-linux1.amherst.edu> wrote:

> 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).
If your max draw, encoding multi-core, say your draw then is 200W, then a 200/.80 = 250W PSU would be optimal.
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