Virtual Performance Counters are a specific type of counters used exclusively within NetCrunch. They are called virtual because they do not directly reference an existing monitored performance counter. A more accurate term for them might be Calculated Counters.
These counters allow the creation of custom metrics by defining arithmetic expressions that use real data collected from monitored device counters (such as SNMP, Windows, Linux, Mac OS X, BSD, or Solaris). The expressions can include addition, subtraction, multiplication, division, and MIN or MAX functions.
In a Virtual Counter definition, you can only use real monitored performance counters of one type (e.g., SNMP, Linux, Mac OS X, BSD, Solaris, or Windows) as variables in the arithmetic expression.
Creating Virtual Performance Counters
- Single Counter Type: When defining a Virtual Counter, you can only use performance counters of one type (e.g., SNMP, Linux, Mac OS X, BSD, Solaris, or Windows) within the arithmetic expression.
- Wizard Assistance: You define a Virtual Performance Counter using the program wizard.
- Using Instances: If instances are used in the definition, you must refer to a virtual instance of the selected real monitored counter, called VCounter. This VCounter will be used in the arithmetic expression as a variable.
Once created, you can use the virtual counters like regular counters in threshold definitions, trend viewer, reports, or events. Virtual counters always start with .NCVC to distinguish them from regular device counters.
Examples of Virtual Performance Counters
-
Average CPU Utilization: - to get a consolidated view of CPU performance across multiple servers:
(Server1_CPU + Server2_CPU + Server3_CPU) / 3 -
Maximum Disk I/O Operations: - to identify the disk with the highest activity:
MAX(Disk1_IOPS, Disk2_IOPS, Disk3_IOPS) -
Combined Disk Read/Write Speed: - to measure overall disk performance:
Disk_Read_Speed + Disk_Write_Speed
These examples show how Virtual Performance Counters can provide more insightful and actionable data than individual performance counters alone.
Note
Please note that you cannot delete a virtual performance counter definition if it is already in use elsewhere in the program.
