It's simple and easy to get Pacemaker's view of the status of members in a cluster – just invoke crm_mon. But what if you want to check on the cluster membership when Pacemaker is not running, or you want to make sure whether Corosync's view of the cluster is identical to …

Often, people deploy the Pacemaker stack in virtual environments for purposes of testing and evaluation. In such environments, it's easy to test Pacemaker's fencing capabilities by tying in with the hypervisor.

This quick howto illustrates how to configure fencing for two virtual cluster nodes hosted on a libvirt/KVM hypervisor …

If you want a Pacemaker cluster to move resources on changes on the network connectivity of an individual node, there are two major steps involved:

• Let Pacemaker monitor connectivity;
• Configure constraints to react on connectivity changes.

Prerequisites

Be sure to run at least Pacemaker 1.0.11 or 1.1 …

Setting up GFS2 in Pacemaker requires configuring the Pacemaker DLM, the Pacemaker GFS control daemon, and a GFS2 filesystem itself.

Prerequisites

GFS2 with Pacemaker integration is supported on Debian (squeeze-backports and up) and Ubuntu (10.04 LTS and up). You'll need the dlm-pcmk, gfs2-tools, and gfs-pcmk packages.

Fencing is imperative …

Ever wonder what meta interleave really means in a Pacemaker clone definition? We'll explain.

The interleave meta attribute is only valid on Pacemaker clone definitions – and their extended version of sorts, master/slave sets. It's not available on primitives and groups. Clones are often used in configurations involving cluster filesystems …