Synchronous Replication Even Across Datacentres
Channel: Linux.conf.au 2014 -- Perth, Australia
Date: 2014-01-17

Presenter(s): Arjen Lentz
URL: https://lca2014.linux.org.au/schedule/30212/view_talk

MariaDB from 5.5 includes Galera Clustering, based on the wsrep library developed by the Finnish company Codership.

Traditionally, synchronous replication requires a two-phase commit process. This works reasonably well within a single datacentre, although performance can still degrade with a larger number of systems in the cluster.

Eventual consistency is another approach, typically utilised in (non-RDBMS) distributed database systems such as Google's BigTable. While valid in many situations, it's unsuitable for some applications and a hassle in others.

Galera uses a different mechanism again, which can crudely be described as "virtual synchrony": generally speaking, all members of the cluster will be updated at the same time as the system initiating the write. This makes application writers very happy. Because fewer communication cycles are required, it can also work across datacentres and even over intercontinental links. This means we can do active-active across multiple datacentres, and that's not just shiny but something many people really want/need.

This talk provides an overview of these different approaches to clustered replication and then delves into the technical detail of how Galera does its magic.

http://lca2014.linux.org.au - http://www.linux.org.au
CC BY-SA - http://creativecommons.org/licenses/by-sa/4.0/legalcode.txt