Information Technology Reference
In-Depth Information
see which VM is the culprit. Unlike in other resxtop views, you can't use V (uppercase only)
here to show only VMs.
Monitoring Disk I/O Statistics with d
Memory and disk I/O are considered the most
important components in your vSphere environment. While memory is important because
it gets exhausted i rst, disk I/O is often overlooked even though bad disk performance will
directly impact the VMs performance.
To monitor disk I/O statistics about each of the disk adapters, press d (lowercase only) and
press u (lowercase only) for disk devices and v (lowercase only) for disk VM. As with some
other views, you can press V (uppercase only) to show only VMs. The columns labeled
READS/s, WRITES/s, MBREAD/s, and MBWRTN/s are most often used to determine disk
loads. Those columns show loads based on reads and writes per second and megabytes read
and written per second.
The resxtop command also lets you view CPU interrupts by pressing i. This command will
show you the device(s) using the interrupt and is a great way to identify VMkernel devices, such
as a vmnic, that might be sharing an interrupt with the Service Console. This sort of interrupt
sharing can impede performance.
Capturing and Playing Back Performance Data with
resxtop
Another great feature of resxtop is the ability to capture performance data for a short period of
time and then play back that data. Using the command vm-support, you can set an interval and
duration for the capture.
Perform the following steps to capture data to be played back on resxtop:
1.
Using PuTTY (Windows) or a terminal window (Mac OS X or Linux), open an SSH ses-
sion to an ESXi host. Note that this requires enabling the ESXi Shell and SSH, both of
which are disabled by default.
2.
Enter the
su -
command to assume root privileges.
3.
While logged in as root or after switching to the root user, change your working direc-
tory to /tmp by issuing the command
cd /tmp
.
4.
Enter the command
vm-support -p -i 10 -d 180
. This creates a resxtop snapshot,
capturing data every 10 seconds, for the duration of 180 seconds.
5.
The resulting i le is a tarball and is compressed with gzip. You must extract it with the
command
tar -xzf esx*.tgz
. This creates a vm-support directory that is called in the
next command.
6.
Run
resxtop -R /vm-support*
to replay the data for analysis.
Now that we've shown you the various tools (alarms, performance charts, vC Ops, and resx-
top) that you will use to monitor performance in a vSphere environment, let's go through the
four major resources—CPU, RAM, network, and disk—and see how to monitor the usage of
these resources.
Monitoring CPU Usage
When monitoring a VM, it's always a good starting point to keep an eye on CPU consumption.
Many VMs started out in life as underperforming physical servers. One of VMware's most
