Xen Monitoring Tools and Techniques

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So far in this book we have focused primarily on the creation of Xen guest domains (domainU). By this stage it is safe to assume that you now have one or more domainU systems up and running on your server or desktop. Given this assumption, this chapter of Xen Virtualization Essentials will be dedicated to providing an overview of the tools and techniques that may be employed to monitor a Xen based environment.

Why Monitor a Xen Environment?

It is important to keep in mind that Xen is an enterprise level environment capable of supporting complex virtualization configurations. As with any complex system it would be naive to assume that the system will run without the occasional performance issues or problem. Deploying Xen virtualization therefore requires an understanding of the tools and techniques necessary to monitor the running environment, identify performance issues and track down problems.

Obtaining Xen Configuration and System Information

Perhaps the most basic step in monitoring a Xen system or isolating a problem is to get a high level overview of the Xen environment and underlying configuration. This information will be of particular importance when requesting help from a vendor or forum. A good way to obtain this information is to use the xm info command. For example, the following example shows output from xm info on a Red Hat Enterprise Linux 5 (RHEL5) system:

xm info
host                   : localhost.localdomain
release                : 2.6.18-53.el5xen
version                : #1 SMP Wed Oct 10 17:06:12 EDT 2007
machine                : i686
nr_cpus                : 1
nr_nodes               : 1
sockets_per_node       : 1
cores_per_socket       : 1
threads_per_core       : 1
cpu_mhz                : 2993
hw_caps                : 0febfbff:20100000:00000000:00000180:0000a015:00000000:00000001
total_memory           : 255
free_memory            : 14
xen_major              : 3
xen_minor              : 1
xen_extra              : .0-53.el5
xen_caps               : xen-3.0-x86_32p 
xen_pagesize           : 4096
platform_params        : virt_start=0xf5800000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)
cc_compile_by          : brewbuilder
cc_compile_domain      : build.redhat.com
cc_compile_date        : Wed Oct 10 16:30:55 EDT 2007
xend_config_format     : 2

Monitoring Xen Performance with XenMon =

The XenMon tool is useful for monitoring the performance Xen domains, particularly when identifying with domains are responsible for the highest I/O or processing loads on a system.

XenMon is started from the command-line using the xenmon.py command. The following figures shows a typical XenMon session:

Monitoring Xen Performance with XenMon