Perhaps one of the more practical uses was figuring out how to scale storage performance when I was at NetApp. Since processors had stopped scaling like they had been in 2001 their CTO challenged me to scale storage performance in terms of IOs per second and total available capacity, without improving the speed of the processors.
The challenge there ended up localized around a couple of really hard sub-problems. One was that Netapp's storage model was file based (rather than block based) and so part of the problem was scaling the operation of a file state machine, and the other serious sub-problem was the creating a reliable way to keeping protocol/process state that was in "flight" in order to recover from failures. Working backwards led to what I ended up calling the "three layer cake" model which split the storage stack into parts that were loosely coherent and tightly coherent.
The challenge there ended up localized around a couple of really hard sub-problems. One was that Netapp's storage model was file based (rather than block based) and so part of the problem was scaling the operation of a file state machine, and the other serious sub-problem was the creating a reliable way to keeping protocol/process state that was in "flight" in order to recover from failures. Working backwards led to what I ended up calling the "three layer cake" model which split the storage stack into parts that were loosely coherent and tightly coherent.