6.0.1

Table Of Contents
Virtual Machines
The virtual machine charts contain information about CPU, disk, memory, network, storage, and fault
tolerance for virtual machines. The help topic for each chart contains information about the data counters
displayed in that chart. The counters available are determined by the collection level set for vCenter Server.
CPU (%)
The CPU (%) chart displays virtual machine CPU usage and ready values.
This chart is located in the Home view of the virtual machine Performance tab.
Table 194. Data Counters
Chart Label Description
Usage Amount of actively used virtual CPU as a percentage of total available CPU.
CPU usage is the average CPU utilization over all available virtual CPUs in the virtual machine.
For example, if a virtual machine with one virtual CPU is running on a host that has four physical CPUs
and the CPU usage is 100%, the virtual machine is using one physical CPU completely.
virtual CPU usage = usagemhz ÷ (number of virtual CPUs × core frequency)
NOTE This is the host's view of the CPU usage, not the guest operating system view.
n
Counter: usage
n
Stats Type: Rate
n
Unit: Percentage (%). Precision is to 1/100%. A value between 0 and 100.
n
Rollup Type: Average (Minimum/Maximum)
n
Collection Level: 1 (4)
Ready Percentage of time that the virtual machine was ready, but could not get scheduled to run on the physical
CPU.
CPU ready time is dependent on the number of virtual machines on the host and their CPU loads. At
collection level 1, the average CPU ready time of all virtual CPUs on the virtual machine is displayed. At
collection level 3, the average CPU ready time of each virtual CPU is also displayed.
n
Counter: ready
n
Stats Type: Rate
n
Unit: Percentage (%)
n
Rollup Type: Summation
n
Collection Level: 1
Chart Analysis
A short spike in CPU usage or CPU ready indicates that you are making the best use of the virtual machine
resources. However, if the CPU usage value for a virtual machine is above 90% and the CPU ready value is
above 20%, performance is being impacted.
If performance is impacted, consider taking the actions listed below.
Table 195. CPU Performance Enhancement Advice
# Resolution
1 Verify that VMware Tools is installed on every virtual machine on the host.
2 Set the CPU reservations for all high-priority virtual machines to guarantee that they receive the CPU cycles
required.
3 Compare the CPU usage value of a virtual machine with the CPU usage of other virtual machines on the host or in
the resource pool. The stacked line chart on the host's Virtual Machine view shows the CPU usage for virtual
machines on the host.
4 Determine whether the high ready time for the virtual machine resulted from its CPU usage time reaching the CPU
limit setting. If so, increase the CPU limit on the virtual machine.
vSphere Monitoring and Performance
68 VMware, Inc.