We all know that when using a cluster based on Galera (Codership) such as Percona XtraDB Cluster (PXC), it is recommended to deploy an odd number of nodes.
The generic answer to this recommendation is that otherwise the risk of having an inconsistent cluster (like split-brain) is higher. (see Get started with Percona XtraDB Cluster – Percona XtraDB Cluster )
As a reminder, when split-brain occurs, a cluster will stop accepting queries, which is what a safe solution should do while waiting for the DBA to review and decide which of the two nodes is the leader. I do not even want to describe the infamous wsrep_provider_options=”pc.ignore_sb = yes”, which has been the cause of many, many nights spent trying to …
[Read more]