What the hell happened in my computer room this afternoon?

[Feek]

I've just installed a Netbotz monitoring system in one of our racks, the unit itself is sitting in the middle of the rack at the back.

Earlier today my Blackberry bleeped and I had a warning that the internal temperature had reached 30.1C. I was in the middle of a BBQ at the time so it wasn't easy to get away but although 30C is high, I wasn't too worried providing it got no higher.

I wanted to get a plot of how the temp had gone over the previous 12 hours so at just after 21:00 I logged on and checked. It was as follows.

http://www.feek.ukfsn.org/temp/internal.png

Yikes, still over 30C. But nothing I can do about it from here, it'll have to be looked at in the morning.

Then I checked the external sensor. It's on a cable hanging out of the top of the rack and over the edge so not in any direct airflow out of the rack.

http://www.feek.ukfsn.org/temp/external.png

WTF? As the internal one went up, the external dropped.

I need to pull the logs to see whether the room was accessed around those times and check the airconditioning as well. We've got a door sensor but it's not fitted yet. It will go on this week!

Any thoughts as to what could have caused the above? it's very strange.

[Garp]

Hmm.. for all that looks dramatic you're only talking a 4 degree change.

Is the sensor hanging out on the hot or cold side of the rack? I would guess hot given its initial recordings up to the 'event' were fairly similar to in rack.

[Feek]

It turns out it was Security. They went in yesterday afternoon and thought that it felt a bit warm so they opened the door. The ambient temperature in the room dropped, but the rack temperature went up. They closed the door at about 5AM and the temps reversed themselves almost instantly.

They won't be doing that again!

But it does raise an important thing and that's that we need to get the aircon upgraded which won't be a small job.

[Garp]

Ahh, aircon can't cope with cooling your entire floor :)
I never understood the point of those slow turning 120mm fans at the top of the cabs in our data centres, but the data centre manager assures me just the slightest bit of negative pressure at the top of the cab causes the heat to rise significantly more effectively.

[Feek]

Our airconditioning was serviced and adjusted today.

Can you tell what time the guy was in?

http://www.ukrm.org/feek/temp/rack-20080517-132445.png

http://www.ukrm.org/feek/temp/room-20080517-132522.png

The red bit on the second image is where it dropped below the low 'alert' temperature of 20.0C and I got some emails through to tell me so I logged on and set the lower limit to 15C.

These graphs make me happier :D

[Mark]

Can you tell what time the guy was in?
Can you tell what he was doing in the 9 minutes between the door opening and the AC getting turned down/off? :)

5C temperature drop certainly looks like a result.

[Feek]

That was probably a bit of discussion as to what could be done, and what was happening.

I've just checked again and here's a new set of plots.

http://www.ukrm.org/feek/temp/rack-20080517-223438.png

http://www.ukrm.org/feek/temp/room-20080517-223838.png

That'll be the aircon cutting in and out :)

[SidewinderINC]

Does a pretty good cycling job :)

I'm not allowed to work in temps that low :p