The libvirt plugin uses the virtualization API libvirt, created by RedHat's Emerging Technology group, to gather statistics about virtualized guests on a system. This way, you can collect CPU, network interface and block device usage for each guest without installing collectd on the guest systems. Because the statistics are received from the hypervisor directly, this works not only with para-virtualized hosts, but with hardware virtualized machines, too.
Other statistics than the ones listed above can not be collected through this plugin. For more detailed statistics you will need to install collectd on each guest.
The plugin can be configured to only collect specific domains, block devices or interfaces. For a full description of available please refer to the libvirt section in the collectd.conf(5) manual page.
<Plugin "libvirt"> Connection "xen:///" RefreshInterval 60 #Domain "name" #BlockDevice "name:device" #InterfaceDevice "name:interface" #IgnoreSelected false HostnameFormat "name" </Plugin>