Remember the terror (or joy, depending on your temperament) as you went up and down, and up and down? Well, just imagine the same thing hapening in your server room.
That's exactly what happened to Patco Construction, one of the largest residential and commercial building firms in the State of Maine. Humidity levels in its server room varied wildly on an hourly basis and swung from 20 percent in winter to 80 percent in summer. Temperature, too, fluctuated up to 10 degrees every hour.
''I didn't need to go to an amusement park to have fun,'' says Tom McDowell, network specialist at Patco Construction. ''I just needed to step into the server room to experience the terror of the server room roller coaster.''
Patco Construction is a $17-million-a-year, full-service construction company. It began building homes in Maine and New Hampshire in 1980. In the mid-80s it expanded into commercial building, focusing on metal pre-engineered and pre-fabricated components that are more cost-effective than most conventional structural designs. Patco constructs low-rise steel buildings for manufacturing, warehousing, school and commercial applications.
Patco's server room has 15 servers, mostly Linux and Windows 2000. In addition, it contains a Cisco switch and a Cisco router, two HP Procurv switches, two D-Link switches and two telephone PBXs. AC is essential in the 120-square-foot space as the server room generates a fantastic amount of heat.
One day, McDowell noticed an interesting phenomenon.
''Some of the hand tools, like wrenches and screwdrivers that had been left in the room for some months, were starting to display specks of rust,'' he says. ''With $100,000 worth of equipment in that room, you can understand how worried I became.''
The underlying architecture of the office caused further concern. Most of the 50 employees in the Patco building depend upon computers that are little more than dumb terminals. Applications and files are all housed on servers.
''If one server went down, it might result in two days of down time,'' says McDowell. ''That could mean many employees are not able to function.''
The network manager decided to buy some environmental monitors to locate the exact source of the problem. He purchased one probe from NetBotz, which is based in Austin, Texas, and a probe from Javica, a distributor of environmental probes based in Sanford, Maine, to monitor temperature and humidity. These probes are simply fastened to the wall and connected to both power and the ethernet.
''The rep from Javica came in, installed the environmental monitor and helped me understand what was happening in our server room environment,'' says McDowell. ''The results were a big surprise.''
Due to his concerns over rusting, McDowell first investigated humidity. With only one day's data collected, a pattern emerged. Every hour, the humidity dove from 80 percent to 60 percent, and then back up to 80, back down to 60, and then back to 80. This pattern repeated 24 hours a day
These results are graphed on the Round Robin Database tool (RRDTool), a system for storing and displaying time-series data which can include SNMP variables, but also any other type of data that can be graphed against time. This is an open source tool developed by Tobi Oetiker that has Linux, UNIX and Mac OSX versions available.
Next, McDowell checked the temperature readings. These revealed a similar picture. The temperature swung between 62 degrees F and 70 degrees. Further, the pattern closely matched that of the humidity graph.
''At about 63 degrees, the AC clicks off to save electricity and to prevent the room from getting too cold to work in,'' notes McDowell. ''However, at that temperature, there is still a lot of humidity in the room, too much in fact during the summer.''
So at that point, McDowell understood why rust was forming on equipment and tools -- the AC wasn't removing all the humidity. When it switched off, the temperature would rise and humidity would return to 80 percent. Patco calculated that it needed to let the AC bring the temperature down to 45 degrees in order to bring the humidity down to the desired levels. However, 45 degrees might be bad for the equipment.
''We would end up with a huge electricity bill, and if we had technicians in there for any length of time, they would have to be wearing gloves and jackets,'' says McDowell. ''Nobody would want to work in an environment like that.''
After gaining a few months of figures, he also spotted another interesting trend. The humidity graph varied from 20 percent in the winter to 80 percent in the summer. Unlike the daily roller coaster, this is a relatively smooth transition from month to month.
''So we have static problems in winter when humidity is too low, and rust developing in summer when it's too high,'' says McDowell. ''The temperature and humidity sensors that Javica provided were invaluable in making us aware of the problem, but now we need to find something that will solve the situation for us.''
Patco is checking into various airflow and humidity-control products. By improving the airflow, McDowell hopes to add some stability. But he realizes that some form of cost-effective humidity control now is essential.
''With better airflow and more controlled humidity, we could maintain a more consistent temperature and humidity,'' says McDowell. ''The eventual goal is to reduce the hourly temperature variance to a few degrees and maintain humidity at a relatively stable level all year.''