# Understanding Perfmon - Time interval/Data Sample • ### Question

• I was wondering if someone could clarify the sampling interval for me.
If I were to monitor bytes sent/sec on a nic using performance/system monitor and set the sampling interval to 5 mins.
Would the results display:
A. what is going through the nic at that exact time.
B. The average of what has gone through the nic over the last 5 minutes (indicating that it has been keeping track)
C. A running total of what has passed through the nic between the last sample and the next interval.
D. other  (if so, please explain)

Saturday, December 19, 2009 4:20 AM

### All replies

• -MnMz19

Sampling interval specifies when the data is collected, this will not be a cumulative average value; this will be the value at that moment in time.

This works in the same manner as a perfmon counter, if your interval was set to 3 seconds you have no clue what the value was between the intervals.

So to answer your question definitively, the answer is A.

Thanks, and good luck.

-Jordan
Wednesday, December 23, 2009 3:52 PM
• It going to depend on the counter:

So for Network Interface\Bytes Sent/sec

Counters by Object

http://msdn.microsoft.com/en-us/library/ms803998.aspx

 Counter Name Description Counter Type Bytes Sent/sec Shows the rate at which bytes are sent over each network adapter. The counted bytes include framing characters. Bytes Sent/sec is a subset of Network Interface\Bytes Total/sec. PERF_COUNTER_COUNTER

Once you have the counter type you can look how it works at:

Counter Types

http://msdn.microsoft.com/en-us/library/ms803989.aspx

PERF_COUNTER_COUNTER

 Description This counter type shows the average number of operations completed during each second of the sample interval. Counters of this type measure time in ticks of the system clock. The F variable represents the number of ticks per second. The value of F is factored into the equation so that the result can be displayed in seconds. Generic type Difference Formula (N1- N0) / ( (D1-D0) / F), where the numerator (N) represents the number of operations performed during the last sample interval, the denominator (D) represents the number of ticks elapsed during the last sample interval, and F is the frequency of the ticks. Average (Nx - N0) / ((Dx - D0) / F) Example System\ File Read Operations/sec

Bruce Adamczak
Monday, January 4, 2010 5:26 PM
• Bruce, you give interesting information, but it does wrongly answer to the question. Moreover it will confuse people.

Even is the Bytes Sent/sec is calculated on a 1 second interval, this will be the value at that moment in time. It will never be an average on the whole sample interval !
Friday, October 28, 2016 4:56 PM