Firefox needs a diagnostic tool to tell when the underlying storage device is too crappy. We could use this info to start making decisions on turning off disk caches, switching cache locations, etc(eg on android we have a choice between internal and external sd). It would also be good to show that to the user via healthreport(eg fhr). It would also be interesting to diagnose speeds of storage hw in the wild. Firefox should send in a distribution of latency of open/close/read/write/fsync along with accompanying device info.