Storage I/O Rate

Given an estimate of cache hit ratio H, the service's storage I/O load is easily derived: for a Web load of $\lambda$ requests per second, the I/O throughput demand $\lambda _S$for storage (in IOPS, or I/O operations per second) is:

$$\lambda_S = \lambda S (1 - H)$$ (2)

The average object size S is given as the number of I/O operations to access an object on a cache miss.