The CPU (MHz) chart displays CPU usage for the cluster.

Cluster Counters

This chart is located in the Home view of the Cluster Performance tab.

Table 1. Data Counters

Chart Label

Description

Usage

Sum of the average CPU usage values, in Megahertz, of all virtual machines in the cluster.

  • Counter: usagemhz

  • Stats Type: Rate

  • Unit: Megahertz (MHz)

  • Rollup Type: Average (Minimum/Maximum)

  • Collection Level: 1 (4)

Total

Total amount of CPU resources available in the cluster. The maximum value is equal to the number of cores multiplied by the frequency of the processors.

For example, a cluster has two hosts, each of which has four CPUs that are 3GHz each, and one virtual machine that has two virtual CPUs.

VM totalmhz = 2 vCPUs * 3000MHz = 6000MHz

Host totalmhz = 4 CPUs * 3000MHz = 12000MHz

Cluster totalmhz = 2 x 4 * 3000MHz = 24000MHz

  • Counter: totalmhz

  • Stats Type: Rate

  • Unit: Megahertz (MHz)

  • Rollup Type: Summation

  • Collection Level: 1

Chart Analysis

A short spike in CPU usage indicates that you are making the best use of cluster resources. However, if the value is constantly high, the CPU demanded is likely greater than the CPU capacity available. A high CPU usage value can lead to increased ready time and processor queuing of the virtual machines on the hosts in the cluster.

If performance is impacted, consider taking the following actions.

Table 2. CPU Performance Enhancement Advice

#

Resolution

1

Verify that VMware Tools is installed on each virtual machine.

2

If the cluster is not a DRS cluster, enable DRS. To enable DRS, perform the following tasks:

  1. Select the cluster, and click the Configure tab.

  2. Under Services, click vSphere DRS.

  3. click Edit.

    An Edit Cluster Settings dialog box opens.

  4. Click Turn ON vSphere DRS, and click OK.

3

If the cluster is a DRS cluster:

  • Increase the number of hosts, and migrate one or more virtual machines to the new host.

  • Check the aggressiveness threshold. If the value is low, increase the threshold. This might help avoid hot spots in the cluster.

4

Migrate one or more virtual machines to a new host.

5

Upgrade the physical CPUs or cores on each host in the cluster if necessary.

6

Enable CPU-saving features, such as TCP Segmentation Offload.

7

Replace software I/O with dedicated hardware, such as iSCSI HBAs or TCP Segmentation Offload NICs.