Key ingredients to achieve effective 1/O asyne l0op nact cachincc 花5 Sources of I/O latency Physical constraints preparing an SSD(~100 us) omoving disk's arm (~10ms) omounting and rotating tapes(1 min) latency amc mig 5/57 S.Ponce-CERNKey ingredients to achieve effective I/O 5 / 57 S. Ponce - CERN async IOopt struct caching c/c latency async msgQ Sources of I/O latency Physical constraints preparing an SSD (∼ 100 ➭s) moving disk’s arm (∼ 10 ms) mounting and rotating tapes (∼ 1 min) Network infrastructure number of switches routers on the way 200 ➭s delay per switch/router “slow” speed of light “speed” of light is slower in a fiber (refractive index 1.47) that gives around 200 m ➭s −1 or 20 cm ns −1 Budapest’s ping time from CERN is ∼21 ms for ∼2500 km