We've been using GNU eatmydata library to removes fsync calls from testing. This was done in the past to speed up our runs on Linux. Right now, in evergreen we link with this library on ubuntu and redhat. It turns out that eatmydata may be feasible on Mac (see https://stackoverflow.com/questions/8217621/eatmydata-on-os-x), as the unit tests run for ~3 hours.

Maybe this, or something equivalent, can be explored on other build variants that don't currently use it, like PPC, Zseries, or even Windows.