How are the metrics calculated in agentless server monitoring?

SNMP server monitoring

Metrics such as CPU, Memory, and Disk utilization are collected via SNMP using the OIDs given below:

Attribute	OID
CPU	.1.3.6.1.2.1.25.3.3.1.2
Memory	.1.3.6.1.2.1.25.5.1.1.2
Disk	.1.3.6.1.2.1.25.2.3.1.6
Free Disk Space (MB)	(.1.3.6.1.2.1.25.2.3.1.4.1*(.1.3.6.1.2.1.25.2.3.1.5.1-.1.3.6.1.2.1.25.2.3.1.6.1))/(1048576)
Used Disk Space (MB)	(.1.3.6.1.2.1.25.2.3.1.4.1*.1.3.6.1.2.1.25.2.3.1.6.1)/(1048576)
Disk Partition	(.1.3.6.1.2.1.25.2.3.1.6.1*100/.1.3.6.1.2.1.25.2.3.1.5.1)
Network	.1.3.6.1.2.1.2.2.1
Processes	.1.3.6.1.2.1.25.4.2.1
Services	Static Services with fixed ports

If you do not see the metrics being displayed in the web client, please check if the server responds to SNMP GET requests for the above mentioned OIDs as described here.

WMI server monitoring

CPU, Memory, and Disk metrics are collected using the queries given below:

Metric	WMI Query
CPU Metrics	SELECT LoadPercentage, DeviceID FROM Win32_Processor
Memory Metrics	SELECT FreePhysicalMemory,TotalVisibleMemorySize FROM Win32_OperatingSystem
Disk Metrics	Select * from Win32_LogicalDisk where DriveType=3 or DriveType=4
Process Metrics	Select * from Win32_Process

You can execute WMI queries as described here.

Individual disk metrics:

Individual disk metrics are collected by executing the Visual Basic Script available in the following path:

{Site24x7 On-Premise Poller installed directory}/NetworkPlus/conf/OpManager/application/scripts/disk.vbs

To test the above, execute the file in the Command Prompt (as Administrator) as follows:

disk.vbs <Target IP/Host Name> <UserName> <Password>