Let's say I have a byte counter metric that increments once per second. If I plot it, I will get a monotonically increasing plot. The Y-axis is labeled 'bytes'.
I want to plot the rate of change of my counter, so I click the "Rate" checkbox. Rate is change per unit time, but what is that unit? What label should the Y-axis have?
The Rate feature is a OpenTSDB query feature. According to the OpenTSDB docs
The rate is the first derivative of the values. It's defined as (v2 - v1) / (t2 - t1). Therefore you will get the rate of change per second. Currently the rate of change between millisecond values defaults to a per second calculation.