Information Technology Reference
In-Depth Information
Upon launch, resxtop defaults to showing CPU utilization, as illustrated in Figure 13.15.
At the top of the screen are summary statistics; below that are statistics for specii c VMs and
VMkernel processes. To show only VMs, press V. Be aware that resxtop, like many Linux com-
mands, is case sensitive, so you'll need to be sure to use an uppercase V in order to toggle the
display of VMs only.
Monitoring CPU usage with c
Two CPU counters of interest to view with resxtop are the
CPU Used (%USED) and Ready Time (%RDY) counters. You can also see these counters in
the VM charts, but with resxtop they are calculated as percentages. The %RDY counter is
also helpful in determining whether you have overallocated CPU resources to the VM. This
might be the case if, for example, you've allocated two vCPUs to a VM that really needs only
a single vCPU. While in CPU mode, you can also press lowercase e to expand a VM's CPU
statistics so that you can see the different components that are using CPU time on behalf of
a VM. This is quite useful in determining what components of a VM may be taking up CPU
capacity.
If you switch away to another resource, press C (uppercase or lowercase) to come back to
the CPU counters display. At any time when you are i nished with resxtop, you can simply
press q (lowercase only) to exit the utility and return to the vMA command prompt.
resxtop Shows Single Hosts Only
Remember, resxtop shows only a single ESXi host. In an environment where vMotion, vSphere
Distributed Resource Scheduler (DRS), and vSphere High Availability (HA) have been deployed, VMs
may move around often. It is possible that while you are monitoring a VM, it is suddenly moved off
the host by a vMotion action. Also be aware of this when capturing performance in batch mode.
Monitoring Memory Usage with m
Memory is one of the most important components of
your ESXi host because this resource is usually one of the i rst to get exhausted.
To monitor memory usage with resxtop, press m (lowercase only). This gives you real-time
statistics about the ESXi host's memory usage in the top portion and the VM's memory usage
in the lower section. As with CPU statistics, you can press V (uppercase only) to show only
VMs. This helps you weed out VMkernel resources when you are trying to isolate a problem
with a VM. The %ACTV counter, which shows current active guest physical memory, is a
useful counter, as are the %ACTVS (slow-moving average for long-term estimates), %ACTVF
(fast-moving average for short-term estimates), %ACTVN (prediction of %ACTV at next sam-
pling), and SWCUR (current swap usage) counters.
Monitoring Network Statistics with n
Networking in a vSphere environment is often
taken for granted, but while your environment grows, you'll learn that keeping an eye on
network performance is essential.
To monitor network statistics about the virtual machine network interface cards (vmnics),
individual VMs, or VMkernel ports used for iSCSI, VMotion, and NFS, press n (lowercase
only). The columns showing network usage include packets transmitted and received and
megabytes transmitted and received for each vmnic or port. Also shown in the DNAME col-
umn are the vSwitches or dvSwitches and, to the left, what is plugged into them, including
VMs, VMkernel, and Service Console ports. If a particular VM is monopolizing the vSwitch,
you can look at the amount of network trafi c on a specii c switch and the individual ports to
