The servers run the hospital's mission-critical radiation therapy system used to treat cancer patients. When the power went out, one server -- in a room lacking emergency power -- immediately went down. But the application kept running with no loss of data or interruption as the other server kept humming along.

At another time, smoke from a fire in one of the server rooms brought a server down, even as the overall system continued running without failure. Overall, the radiation therapy system has maintained "better than 99.999 percent uptime," Michaelson said. "We're very happy with its performance."

Littleton, Mass.-based Marathon hopes the latest iteration of its nearly-crash-proof technology will reach an even wider audience. Yesterday, the company launched EverRun HA, which it claims can provide nearly 100 percent uptime for Windows-based clusters. EverRun HA follows the two other applications Marathon has released since its comeback from bankruptcy in January 2004: EverRun Splitsite, which helps servers -- even if they're many miles apart-- replicate data and back up operations, and EverRun FT.

Installed on an identical pair of Windows single- or dual-processor servers, EverRun FT essentially runs an application on both machines simultaneously while using a virtualized layer to create the appearance of a single server, according to Gary Phillips, CEO of Marathon. That eases deployment of applications that are not specially written to divvy up workloads among multiple processors or machines and guarantees virtually no downtime.

EverRun HA is more flexible. Users can deploy an application to run over small groups of Windows servers, including racks of blade servers -- even those with multiple processors. The tradeoff is that EverRun HA guarantees only the industry standard of 99.999 percent uptime, or high availability, instead of true fault-tolerance.