Joe Prisco, a senior systems and technology group engineer at IBM, spoke Sunday, Jan. 26, at the ASHRAE Winter Conference in Chicago. He and two IBM colleagues – Prabjit Singh and Roger Schmidt -- wrote a paper on data center particulate and gaseous contamination.
Any kind of data center contamination -- and there are several types -- can cause problems, said Prisco. He started with data center dust, saying it could be separated into "chemically inert dust" and "corrosive dust."
Chemically inert dust is similar to household dust, and when it starts clogging server intake valves and other small openings, it can affect thermal efficiency, cooling efficiency, and the airflow through heat sinks in electronic components. It can also lead to overheating of power connectors for tape and optical media drives, he said.
Showing a picture of the dust, Prisco pointed out that there was "contamination evidence on covers and intakes."
"It's like a dust bunny is forming," he said.
Corrosive data center dust contains ionic chemical compounds like sulfur and chlorine salts that, when wet, get corrosive. When bridges form between two conductive patterns, Prisco said that short-circuiting can result.
After the session, Prisco added that a lot of the data center contamination comes from IT equipment being delivered in smaller and smaller footprints.
"The openings get smaller, and so the opportunities for bridging are there," he said. "Dust can pile up more easily."
Gaseous contamination and corrosion can come from outside gases -- sulfur dioxide, hydrogen sulfide and nitrogen dioxide -- that make their way into data centers. When two or more of these gases contact one another, he said "you can have a synergy of gases that compound the effect."
To monitor gases, Prisco and the other researchers used "copper coupons" – which look like blank server nameplates. Over time the copper builds a film of corrosion on it, which can be measured.Data center contamination and air-side economizers
Overall, Prisco recommended monitoring data center dust and gaseous contamination. But in particular he suggested that those using or considering air-side economizers should monitor carefully.
"If you're looking into air-side economizers, which I know a lot of people are doing, it would be a good idea to start doing real-time monitoring of dust," he said, later adding that "I'm not saying don't use them, but you need to be careful about monitoring the dust and gaseous contaminants."
William Tschudi, a member of the Lawrence Berkeley National Laboratory (LBNL), took issue with that., however Tschudi was instrumental in a 2007 LBNL study that found that cooling data centers with outside air could save money and wouldn't ruin IT equipment. LBNL found that compounds called hygroscopic salts, when combined with high humidity, can cause equipment to shut down. But Tschudi said filtration systems in most data centers do just fine in keeping contaminants out.
According to the report, "IT equipment reliability degradation due to outdoor contamination appears to be a poor justification for not using economizers in data centers."
Yesterday Tschudi questioned the timeline of data center dust and gaseous contamination. In particular, he was interested in whether corrosion could be strong enough to shorten the normal server refresh cycle.
Prisco said that it all depends on the environment, but that he's seen situations in which computer components fail at a fast rate. He then stressed that he thinks monitoring of data center contamination should be done with all data centers, not just those with air-side economizers. He also said monitoring for contamination could prevent corrosion, whereas once the contamination is in there, it can get difficult to clean it without augmenting the problem.