When carrying out benchmarks, you are ultimately measuring the result of latency. All other forms of benchmarking metrics, including IOPS, MBps, or even higher level application metrics, are derived from the latency of that request.
IOPS are the number of I/O requests done in a second; the latency of each request directly effects the possible IOPS and can be seen by this formula:
An average latency of 2 milliseconds per request will result in roughly 500 IOPS assuming each request is submitted in a synchronous fashion:
1/0.002 = 500
MBps is simply the number of IOPS multiplied by the I/O size:
500 IOPS * 64 KB = 32,000 KBps
It should be clear that when you are carrying out benchmarks, you are actually measuring the end result of a latency. Therefore, any tuning that you are carrying out should be done to reduce end-to-end latency for each I/O request.
Before moving on to looking at how to benchmark various...
