1.4.3 Monitoring the CPU resource

This subsection explains how to monitor the CPU resource of a VMware system.

Organization of this subsection

(1) Overview
(2) Monitoring examples
(3) Other monitoring examples

(1) Overview

In a VMware system, multiple virtual machines share the physical server's CPU. The CPU resource allocated to each virtual machine is called a virtual CPU. The OS running on a virtual machine recognizes a virtual CPU as a normal physical CPU.

The CPU resource of the physical server is distributed according to each virtual machine's CPU resource requirement. However, if the combined total of the CPU resource requirements for the individual virtual machines exceeds the CPU resource on the physical server, the required amount of CPU resource cannot be distributed, resulting in a virtual CPU resource shortage. This adversely affects the performance of the virtual machine.

The schematic diagram below shows a state in which a virtual CPU resource shortage has occurred.

Figure 1‒11: Schematic diagram of a virtual CPU resource shortage

By monitoring CPU performance data, you can detect such performance deterioration in the virtual machines, and thus you can take appropriate corrective action.

Furthermore, in a virtual environment all physical devices are virtualized, such as memory, disks, and network interfaces. The CPU performs this virtualization of physical devices. Therefore, the CPU resource is an important resource that also affects the performance of other virtual devices.

The following four records are used to monitor the CPU resource. For details about records, see 5. Records.

PI record

This record is used to monitor the performance data of the physical server's CPU.
PI_HCI record

This record is used to monitor the performance data of each core of the physical CPU.
PI_VI record

This record is used to monitor the performance data of the CPU that is being used by each virtual machine.
PI_VCI record

This record is used to monitor the performance data of each virtual CPU.

The following figure shows the range of performance data collected in each record.

Figure 1‒12: Range of performance data collected in each record

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(2) Monitoring examples

Using CPU resource monitoring on virtual machines vhost1 and vhost2 as an example, this subsection explains the factors that cause insufficient CPU resources, and how to solve this problem. The following figure shows the items monitored here and the flow of actions to take.

Figure 1‒13: Monitored items and flow of actions

(a) Example of monitoring CPU insufficiency in a virtual machine

You can monitor the virtual machine's CPU insufficiency in the Insufficient % field of the PI_VI record. If a sufficient amount of CPU resources have been allocated to the virtual machine, the CPU insufficiency approaches 0%. Note that you can monitor this item with an alarm provided in a monitoring template.

The figure below shows an example of monitoring CPU insufficiency in a virtual machine.

Figure 1‒14: CPU insufficiency monitoring example

Monitoring template report to be checked: VM CPU Insufficient
Monitoring template alarm to be checked: VM CPU Insufficient

In this example, there appears to be severe insufficiency in the CPU resource of vhost2.

In this case, reassess the configuration information of the virtual machine. If the CPU insufficiency is still high even after the configuration information has been reassessed, consider either adding a CPU to the physical server or adding a physical server.

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(3) Other monitoring examples

Monitoring examples follow that use monitoring templates other than those explained in 1.4.3(2) Monitoring examples.

(a) Checking the physical server's CPU usage status

■ Report that displays a physical server's CPU usage status

Figure 1‒15: Example of monitoring a physical server's CPU usage status

Monitoring template report to be checked: Host CPU Used Status

In this report, a drill-down feature is provided on the reports stored in the Troubleshooting/Recent Past folder. Clicking a virtual machine's usage plane on the graph displays the next report.

■ Report that displays a virtual machine's usage of a physical server's CPU

Figure 1‒16: Example of monitoring a virtual machine's usage of a physical server's CPU

Monitoring template report to be checked: VM CPU Used Status

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