[CentOS] OT: hardware question

On 9/16/2014 14:39, m.roth at 5-cent.us wrote:
> Warren Young wrote:
>> On 9/16/2014 13:29, m.roth at 5-cent.us wrote:
>>>
>>>      Opinions on which slot to use?
>>
>> My opinion is that you should read "Hot Air Rises and Heat Sinks:
>> Everything You Know About Cooling Electronics Is Wrong" by Tony
>> Kordyban.  It is quite readable, for all that it is a serious EE book.
>
> My degree's in CIS, not EE, so I never got into that. Should I assume that
> you are an EE?

No, I just play one on the Internet.

> If so, you could give me an opinion....

I'm trying to tell you that a true EE would not give you an "opinion." 
One might give you a *guess* based on having done similar experiments or 
thermal modeling work, or one might insist on doing the experiment.

An experienced EE giving you a guess should couch it in plenty of 
warnings, since so much about success here is contingent:

- What is the operating environment temperature now?

- What will the temp be on the day when the site power goes down, 
cutting the aircon, while the server room keeps running on UPS, and the 
electronic door locks stay locked because *that* UPS is separate and 
someone forgot to check the battery, so it fell over as soon as the wall 
outlet flatlined?

- How many fans do you have in the case?

- Is it better if you add another, or worse?

Yes, it could be worse.  One of the war stories in the book tells the 
tale of a problem device that wouldn't keep cool enough with a single 
case fan, so they added a second, which made airflow worse because it 
required them to add some really big holes in the case right next to the 
first fan, so a lot of the air went in one hole and right out the other.

Another war story, from personal experience: a workstation from a 
big-name manufacturer which ran wonderfully with the case closed up, but 
when you let all that cool outside air in through the side panel, it 
went into thermal lock-up because you'd disrupted the carefully-designed 
airflow channels.

The correct answer isn't always intuitively correct.

>> Or, you can do the experiment yourself.  You have the equipment, you
>> have the environment, and you have lm_sensors.  Try it both ways, and
>
> No, I cannot "do the experiment". I've got to get these racked and up and
> running, for my users to use. They're not my toys....

You can't spend two hours to run them under load, one hour in each 
configuration?  These servers have to be production ready two minutes 
after first power-on?