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Max Operating Temperature

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Pete Randall
Outstanding Contributor

Max Operating Temperature

Our 22 year old air conditioning system needs work. Rather than wait until the weekend when we might be able to shut things down to survive, the KIC (kumquats in charge) have decided they can save money by doing this during the week - BUT, we have to keep the systems up and running.

From what I've been able to find, operating temperature of most servers and arrays ranges from 5 to 40 degrees centigrade (41 to 104 Farenheit) with recommended ranges of 20 to 25.5 (68 to 78). What I have been unable to find out is whether this is ambient air temperature in the room, or inside the rack, or inside the server cabinet itself. My assumption would be that this is room temperature. Can anyone clarify? And does anyone have a recommendation on just how high they would be willing to risk?

TIA

Pete

Pete
15 REPLIES
Ken Hubnik_2
Honored Contributor

Re: Max Operating Temperature

If it gets in the 90 degree range then they start coming down. Trust me I know from experience.
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

Ken,

Is that room temp?

Pete

Pete
Ken Hubnik_2
Honored Contributor

Re: Max Operating Temperature

This is what the thermometer hanging on the wall next to the rows of racks was reading.
Jeff Schussele
Honored Contributor
Solution

Re: Max Operating Temperature

Hi Pete,

Yup, that's ambient air temp in the room. It's several degrees centigrade higher in the cabinet & probably several more in the system itself.
My rule of thumb is - If it's uncomfortable for a human in the data center, it's going to be trouble for the systems.

Cheers,
Jeff

P.S. Good Luck on trying to keep the PHBs from making a stupid decision on this. Remind them how much those systems cost & the fact that HP can choose not to cover damage caused by overheating under warranty or maintenance.
PERSEVERANCE -- Remember, whatever does not kill you only makes you stronger!
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

OK, Thanks guys.

And, Jeff, don't worry - I already told them.

Pete

Pete
John Poff
Honored Contributor

Re: Max Operating Temperature

Hi Pete,

The site prep guides for your boxes will give you guidelines on operating temperature ranges. Most of the ones I have seen say 68-80 degrees F.

I used to have to sit in a data center full time here, and my boss loved to keep it about 50 degrees in there. He thought it was funny, and I was freezing! I finally dug up a site prep manual for a V-class box we had in there and showed him the range was 68-80 degrees. I told him he was running it too cold and HP might not work on it if it broke, [yeah, sure!]. He finally relented and eased up the temperature to the point that I didn't have to wear a coat all day.

JP
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

John,

Yeah, I saw your reply in that other thread. Unfortunately, my dilemna is at the other end of the temperature range. I do sympatize though - years ago I used to cut meat for a living and I know EXACTLY what it's like.


Pete

Pete
John Bolene
Honored Contributor

Re: Max Operating Temperature

It is air temperature in the room itself.

Our specs....
The air under the floor is normally around 60-65 F. The temp above the floor is 70 - 75 F.

We have sensors that shutdown the power to computers when the air temp gets to 85 F. This was due to the time that the air shutdown and when it got to 90 or so, the computers shutdown from over temp. This took about 10 minutes from the time the air quit.

You can shutdown non-critical devices such as monitors and tape drives which make quite a bit of heat to reduce the heat buildup.
It is always a good day when you are launching rockets! http://tripolioklahoma.org, Mostly Missiles http://mostlymissiles.com
John Poff
Honored Contributor

Re: Max Operating Temperature

Pete,

In that same, small, data center we eventually crammed in 3 V-class boxes, about 8 or 9 K-class boxes, and three EMC arrays. The A/C units could barely keep it around 80 degrees, so we had to rent a couple of portable A/C units to keep things cool for a few months until we could move to a new data center. We were able to rent them from a local equipment place and they did a good job. Maybe something like that might get you through the repairs on your main unit? Or will your KICs spring for the expense? If not, maybe you could get a couple of fans and some big blocks of ice? :)

JP
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

John,

Thanks. I'm thinking of 85 as the limit. We did a test today and I think we can stay under that.


JP,

I'd thought of using ice - kind of reminds me of having one of the old water-cooled mainframes. Talk about a giant step backwards. We're working with the air conditioner folks to see what they can offer to assist us (hopefully at minimal expense).


Pete

Pete
Eugeny Brychkov
Honored Contributor

Re: Max Operating Temperature

If room has temperature about 25C and it's not 'overloaded' with equipment, then usual issue I find on customer sites is improper air flow. The main rule says that equipment takes cool air from the front and throws hot air from the rear (or top). So it's logical to have conditioner/holes in the floor in front of the rack, and hot air drain pipe at the rear of rack. If doing in wrong way, feeding cold air from the rear and getting air from the front then be sure equipment will overheat even if room has 'average' temperature 20C (looking at wall's thermometer)
Eugeny
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

Thanks, Eugeny. We will be forcing as much air as we can at the front of the servers.

Pete

Pete
Chris Vail
Honored Contributor

Re: Max Operating Temperature

YO DUD-E!
This is a bad idea! Our protocols here require us to shed load at 85 degrees F. That means if our data center loses all three of its A/C units, we have to start shutting down systems when the ambient temperature hits 85. With the 300+ machines in the data center, this takes less than 5 minutes....ask me how I know..

The reason for this is simple: reliability. At higher temperatures, silicon doesn't break but it does become unreliable. So perhaps at 90 degrees, 99.999% of math operations are reasonably accurate. Multiply that times 5.5 million transactions, and suddenly 5500 people get a bill that doesn't add up.

There's a curve involved: at 95 degrees, the reliability is down to 99.9% or so, at 96 degrees, 99%, at 97 degrees, 98% etc.. So technically, the machines may work, but you can't depend on them. Actually, some power supplies will start turning themselves off around 95 degrees or so, because they measure their internal temperature, not external.

Let me strongly urge you to get the KIC's to spring for some rental A/C units, and a lot of fans. At the very worse: go buy a couple thousand pounds of ice and blow the hot room air over it to cool the data center. I've done this: several big galvanized tubs of ice and A LOT of very powerful fans to force circulate the air. I've also hung rental A/C units in the doorway of the data center, with plastic sheets under them to catch the drips.

This can cause SERIOUS problems for your reliability. If you can't take the systems down, then get some source of cool air for them.


Chris
John Payne_2
Honored Contributor

Re: Max Operating Temperature

While we were building our new data center, they had to cut the chilled water in our old building for the new one. Our operations manager at the time thought it was a great idea to bring in a couple of large swamp coolers to keep the temp down. This caused me to have to go to the geography department on campus so I could borrow a wet bulb thermometer. (Most stuff looks for a dry bulb and wet bulb temp...) We started under the barrier, luckily.

During the same outage, one of our part-time student operators decided that the temperature at the back of our full rack of A500's was too hot. He put a fan at the back of the servers pointing directly into the servers. We fried 3 A500's all at the same time since the hot exhaust air was being blown back into the server.

(I guess what I am saying is that while you are up at the edge of the temperature range, make sure your circulation is good, that way you don't end up with an isolated area where you have the heat building up. With enough fans blowing, you can get pretty much the entire room's temp to rise all together and have less hot spots. We used carpet fans to do this, mostly...)

Hope it helps.

(And good luck)

John
Spoon!!!!
Pete Randall
Outstanding Contributor

Re: Max Operating Temperature

OK, Thanks for all your inputs - here's the plan.

We ran a test yesterday. Turned the A/C off. Blocked open the doors and put fans in them. Directed fans at the front of the server racks. Put a fan in the elevator door trying to exhaust hot air up the elevator shaft. After 3 hours, the room temp was still holding at right around 80. What was concerning me was the fact that exhaust air coming out the back of my N-class was 88, sometimes 89 degress.

Since you've convinced me that it's room temp that matters, I think we can do this. For the real thing, since we don't know how long it will be, we'll spread even more fans around, turn off all non-essential equipment and wear our shorts and sandals.

Case closed.

Wish us luck,
Pete

Pete