Xen Monitoring Tools and Techniques
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: