Proper definition of IOPS

[vitalyisaev2]

Hello, could you please check the definition of IOPS. In this article it is said that

r/s & w/s- Read/Write requests (after merges) per-second. Their sum is the IOPS!

But if you have a look at iostat source code, you'll see that r/s is defined as a difference between two rd_ios:

			/* r/s */
			cprintf_f(NO_UNIT, 1, 7, 2,
				  S_VALUE(ioj->rd_ios, ioi->rd_ios, itv));

whereas rd_ios is defined as

	/* # of read operations issued to the device */
	unsigned long rd_ios		__attribute__ ((packed));

so rd_ios has nothing to do with merges.

Therefore, r/s reflects the rate of requests issued, but yet not merged. This runs counter to your definition of IOPS.