[Pacemaker] Announcing Pacemaker Remote - extending high availability outside the cluster stack

[David Vossel]

Hi,

I'm excited to announce the initial development phase of the Pacemaker Remote daemon is complete and ready for testing in Pacemaker v1.1.10rc2

Below is the first draft of a deployment guide that outlines the initial supported Pacemaker Remote use-cases and provides walk-through examples.  Note however that Fedora 18 does not have the pacemaker-remote subpackage rpm available even though I do reference it in the documentation (this will be changed in a future draft) You'll have to use the 1.1.10rc2 tag in github for now.

Documentation: http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Remote/index.html

For those of you unfamiliar with Pacemake Remote, the pacemaker_remote service is a new daemon introduced in Pacemaker v1.1.10 that allows nodes not running the cluster stack (pacemaker+corosync) to integrate into the cluster and have the cluster manage their resources just as if they were a real cluster node. This means that Pacemaker clusters are now capable of managing both launching virtual environments (KVM/LXC) as well as launching the resources that live within those virtual environments without requiring the virtual environments to run pacemaker or corosync.

Usage of the pacemaker_remote daemon is currently limited to virtual guests such as KVM and Linux Containers, but several future enhancements to include additional use-cases are in the works.  These planned future enhancements include the following.

- Libvirt Sandbox Support
Once the libvirt-sandbox project is integrated with pacemaker_remote, we will gain the ability to preform per-resource linux container isolation with very little performance impact.  This functionality will allow resources living on a single node to be isolated from one another.  At that point CPU and memory limits could be set per-resource in the cluster dynamically just using the cluster config.

- Bare-metal Support
The pacemaker_remote daemon already has the ability to run on bare-metal hardware nodes, but the policy engine logic for integrating bare-metal nodes is not complete.  There are some complications involved with understanding a bare-metal node's state that virtual nodes don't have.  Once this logic is complete, pacemaker will be able to integrate bare-metal nodes in the same way virtual remote-nodes currently are. Some special considerations for fencing will need to be addressed.

- Virtual Remote-node Migration Support
Pacemaker's policy engine is limited in its ability to perform live migrations of KVM resources when resource dependencies are involved.  This limitation affects how resources living within a KVM remote-node are handled when a live migration takes place.  Currently when a live migration is performed on a KVM remote-node, all the resources within that remote-node have to be stopped before the migration takes place and started once again after migration has finished.  This policy engine limitation is fully explained in this bug report, http://bugs.clusterlabs.org/show_bug.cgi?id=5055#c3 

--
David Vossel <dvossel at redhat.com>
irc: dvossel on irc.freenode.net