Database architecture#

Get answers to common technical questions about database architecture for Rackspace Private Cloud Powered By OpenStack (RPCO) 14.0.

Why does RPCO use MariaDB with Galera?

Rackspace DBAs are familiar with MariaDB with Galera, and RPCO support can use this knowledge to better support customers.

What are the requirements and restrictions for a MariaDB with Galera database cluster?

The cluster must contain at least three database nodes. RPCO architecture has three infrastructure nodes. and one database container is deployed on each node.

MariaDB with Galera clusters with an odd number of nodes function more effectively than clusters with an even number. A cluster with an even number of nodes is possible, but we do not recommend it.

For more information, see How is the cluster scaled up?.

How does the database cluster behave when a node fails?

If the failure is not a catastrophic failure of all nodes in the cluster, the cluster handles the failure gracefully.

** How does a cluster recover from node failure?**

Node failure recovery is documented in the RPCO Operations Guide.

How is the cluster scaled up?

Scaling the cluster must be done in odd numbers. For example, when expanding from three nodes, you can expand to five nodes, but not four. Even numbers of nodes can cause a "split brain" condition within the cluster.

The cluster is scaled by simply adding new nodes to it. Galera initiates data replication from within the existing nodes in the cluster, and the expansion should be seamless.