3 / 6 Latency, Throughput & The Numbers

Four Ways To Fetch

You need one record on the read path and have four candidate designs, one per option below. Cost each one using the standard reference figures: in-datacenter round trip 500 us, random 4 KB SSD read 150 us, 1 MB sequential from SSD 1 ms, 1 MB sequential from memory 250 us, single spinning-disk seek 10 ms.

Which design has the lowest expected latency?

A

Four in-datacenter round trips, then 1 MB read sequentially from memory

B

Two in-datacenter round trips, then one random 4 KB read from SSD

C

One spinning-disk seek

D

One in-datacenter round trip, then 1 MB read sequentially from SSD