High availability provides continuous operation to a system or components set through an extended length of time. The Red Hat Enterprise Linux OpenStack Platform director provides high availability to an OpenStack Platform environment through the use of a Controller node cluster. The director installs a set of the same components on each Controller node and manages them as one whole service. Having a cluster provides a fallback in case of operational failures on a single Controller node. This provides OpenStack users with a certain degree of continuous operation.
The OpenStack Platform director uses some key pieces of software to manage components on the Controller node:
Pacemaker - Pacemaker is a cluster resource manager. Pacemaker manages and monitors the availability of OpenStack components across all machines in a cluster.
HA Proxy - Provides load balancing and proxy services to the cluster.
Galera - Provides replication of the OpenStack Platform database across the cluster.
Memcached - Provides database caching.
OpenStack Platform director automatically configures the bulk of high availability on Controller nodes. However, the nodes require some manual configuration to enable fencing and power management controls. This guide includes these instructions.