Cold Aisle Containment in our server room

On Thursday 10 March 2011, we installed a so-called Cold Aisle Containment in the server room shared by the Department of Computer Science and HIIT. This is a rustic contraption made from transparent PE plastic, air-conditioning tubes, and a great deal of duct tape. It cuts back on the need to cool the server room very efficiently, as the air-tight plastic stops the intake and exhaust air from the servers from mixing.


I videoed the setup before the change and after. The video may look like our server room is starting to resemble one of those biospheres that were popular in the 1990s. The advantage with transparent plastic as building material is that it puffs out with pressure, so now our maintenance team can monitor the cooling capacity of the computer room air conditioners (CRAC) by keeping an eye on the surface of the plastic. In this way, the CRACs will produce exactly as much cool air as the servers need.

Before installing the plastic bubbles in the server room, the CRACs were running full blast all the time. One of them pushed 15-degree (C) intake air under the floor, which became 19-21 degrees when it hit the servers because of the mixing of the air flows.At the end of our three hours of hard work this changed considerably, as the flow of exhaust air became more efficient, making work in the server room much more humane.

The intake air to the servers used to be 20 degrees, but now we need much less cooling capacity. We were able to shut down one CRAC completely and crank up two others 7 degrees. To adjust the last two devices, we need some special tools that we are still waiting for. We will continue to adjust the CRACs, as we are aiming at intake air of 22 degrees and to turn off one more CRAC unit.

Servers in the cold

In addition to optimising the server room, we have been running (other) servers outside since February 2010. At this moment, there is a 26U rack placed on the roof terrace of Exactum. It is protected from water and snow by a kind of cell. You can admire its winking lights at night in the images from the Exactum camera:


We are monitoring the servers constantly, and they are part of the Folding@home calculation. In addition, anyone can ask about the inner temperatures of the servers via a Twitter feed set up to monitor them. Twitter is in a state of perpetual beta, so more features are on the way.


The intake server air is not filtered in any way. The most frequently asked question is, whether the moisture condensing inside the servers harms them. However, the condensation works in reverse, since the servers are cooled by air, so they are always warmer than the air around them. The next most frequent question is whether we could build a sauna with the exhaust air from the servers. We will return to this question in the near future.

If this or any other projects seem interesting to you, you can learn more on Thursday 17 March at the event "Science in the best of company" during the demo session at 17:30-20.


- Researcher Mikko Pervilä

You can also follow our research in our blog at

Created date

17.03.2011 - 13:35

Unique open online programming course starts again at Helsinki University

This is the fifth year in a row that the massive open online course (MOOC) will start at the University of Helsinki. Finns can take the course just for fun, as a part of their upper-secondary education, or even as an entrance exam to the university.

The course is free of charge, and it is so basic that students with no experience of programming can follow it.

Sasu Tarkoma new head of the Department of Computer Science

Since Jukka Paakki announced that he will step down from the post of head of the department on 1 January 2016, Professor Sasu Tarkoma has been elected the new head for the period 1 January 2016-31 December 2017. There were a total of 7 applicants for the position, out of whom the rector decided to appoint Tarkoma on the basis of the proposal by the dean of the Faculty of Science.

The staff of the department would like to congratulate Sasu and wish him success in his new duties. This is a good opportunity to ask our new leader some questions.

The university’s team Game of Nolife won Western European programming contest for students

In the finals in Thailand in spring 2016, the students from the University of Helsinki will face the best teams in the world.

The University of Helsinki has won the inter-university NWERC 2015 programming contest that was held in Linköping recently. It was attended by 95 teams from Western Europe. The Game of Nolife team from the University of Helsinki consisted of computer-science and maths students Tuukka Korhonen, Olli Hirviniemi and Otte Heinävaara.

The Carat research team has published a dataset focusing on collaborative energy diagnostics of mobile devices and applications



The Carat research team from University of Helsinki publishes a dataset from the Carat project ( focusing on collaborative energy diagnostics of mobile devices and applications. The dataset was presented at the IEEE PerCom’15 conference last spring in the publication "Energy Modeling of System Settings: A Crowdsourced Approach" that won the Marc Weiser Best Paper Award given at the conference.