He referred to RAID arrays and ECC memory as hardware devices which, when they encounter errors, can correct them on the fly.

"Correcting bad software on the fly surely should be easier than correcting bad hardware. So I think we need to go in the direction of self healing software," he said. ---PB--- To achieve a Lifetime Failure of zero, he said systems needed to be small. This should start with minimizing the code in the OS kernel, which he also said needed to be modular.

The next step is to isolate components such as drives and file systems so that problems, should they arise, can't spread.

On this matter, Tanenbaum referred to the Principle of Least Authority (POLA): "Don't give something more authority than it needs." In this instance, the failure of one component should not crash other components in the OS.

RAID's self healing ability was a perfect illustration: "If one drive fails it shouldn't pollute the other drives."