About I/O rates and transfer rates (traffic)

Server Priority Manager runs based on the I/O rates and data transfer rates, also called traffic, measured by Performance Monitor. Performance Monitor measures I/O rates and transfer rates every second, and calculates the average I/O rate and the average transfer rate for every sampling interval (specified between 1 and 15 minutes) regularly. These traffic statistics reveal the number of I/Os and amount of data being processed through the ports.

Suppose that 1 minute is specified as the sampling interval and the I/O rate at port 1-A changes as shown in Graph 1 below. When you use Performance Monitor to display the I/O rate graph for 1A, the line in the graph indicates changes in the average I/O rate calculated every minute (see Graph 2). If you select the Detail check box in the Performance Monitor windows, the graph displays changes in the maximum, average, and minimum I/O rates in one minute (see Graph 3).

Using Server Priority Manager you can apply upper limits and thresholds to the average I/O rate or average transfer rate per sampling interval. For example, in the following figures, if you set an upper limit of 150 I/Os to port 1A, the highest data point in the line CL1-A in Graph 2 and in the line Ave. (1 min) in Graph 3 is approximately 150 I/Os. It is possible that the lines Max (1 min.) and Min (1 min.) in Graph 3 might exceed the upper limit.

Graph 1: actual I/O rate (measured every second)

Graph 2: I/O rate displayed in Performance Monitor

Graph 3: detailed I/O rate displayed in Performance Monitor