The Philippine government's official weather service, PAGASA, has replaced its SGI supercomputer with a clustered Debian Linux system that can process information vital to protection against typhoons, floods, droughts, tsunamis and other wild weather conditions at a fraction of the cost.

The cluster includes eight PCs running as a single node, connected via a gigabit switch, each with dual 64-bit Intel Xeon processors running the Debian Linux OS.

"We tried several Linux flavours, including Red Hat, Mandrake, Fedora etc," said Alan Pineda, head of ICT and flood forecasting at PAGASA.

"Our ICT group came out with Debian as the most stable in servers, especially when things are being done pretty much in automatic mode. In our workstations the preference among programmers is Ubuntu, which is basically Debian-based," he said.

The major motivation for migrating to an open source based system was cost. Previously, for almost a decade PAGASA used an SGI Irix supercomputer that cost over P200,000 (AUD$5200) a month to run. Since September 2007, the Debian Linux cluster has dropped that monthly figure down to around P10,000 (AUD$260).

"The other motivation was to increase computing power with less capitilisation. With Irix, our capitilisation was about P25 million (AUD$655,000). With the Debian cluster we spent around P2 million (AUD$52,000) including the migration cost and training," Pineda said.

"It doesn't make a dent in our budget; it's very negligible."

Pineda said PAGASA also wanted to implement a system which is very scalable.

All in all PAGASA uses 32 clustered processors, with 16 devoted to R & D and 16 for operational purposes.
The cluster works as part of the Philippine Interactive Communications Weather Information Network (PICWIN) which provides weather forecasting and an automatic warning system.

PICWIN was designed by the Advanced Science and Technology Institute (ASTI), part of the Philippine government's Department of Science and Technology.

All of the equipment used for PICWIN's data gathering comes off-the-shelf, including laptops and mobile phones to transmit weather data such as temperature, humidity, rainfall, cloud formation and atmospheric pressure from field stations via SMS into PAGASA's central database.

"When all data is collected, both locally and internationally through the Global Telecommunications System (GTS), the cluster computer ingests all of this data and computes forecasts using models of the atmosphere.

"These are then analysed by weather forecasters and converted into meaningful information. Outputs are graphically summarized in our Web site in real-time," Pineda explains

The operational cluster is designed to calculate 3-day weather forecasts twice daily, and uses a variety of free and open source meteorological software.

"All that we are running is open source, like the German High Resolution Model (HRM), MM5, ETA. What was even surprising to us is that Intel FORTRAN is also free of charge, including all the math libraries and MPIC system," he said.

"We are quite happy with the results so far, considering we haven't applied assimilation of our radar and satellite products. We believe that as soon as these things are done, we can become even more confident in our long-term forecasts," Pineda said.