Key components

EDB Postgres Distributed provides loosely-coupled multi-master logical replicationusing a mesh topology. This means that you can write to any server and thechanges are sent directly, row-by-row to all theother servers that are part of the same mesh.

EDB Postgres Distributed consists of several components that make the wholecluster work.

Postgres server

Three different Postgres distributions can be used:

• Standard PostgreSQL Statistics Views - open source

• EDB Postgres Extended Server - PostgreSQL compatible and optimized for replication

• EDB Postgres Advanced Server - Oracle compatible, optimized for replication, and

additional enterprise features

What Postgres distribution and version is right for you depends on the features you need.See the feature matrix in Choosing a Postgres distribution for detailed comparison.

Postgres extensions

BDR

A Postgres server with the BDR extension installed is referred to as a BDRnode. BDR nodes can be either data nodes or witness nodes.

Witness nodes don’t participate in data replication and are only used as atie-breaker for consensus.

!!!note “pglogical3”

Older versions of BDR (3.6/3.7) depended on pglogical3 to provide the replicationchannel upon which BDR builds. It is no longer used.

HARP is connection management tool for a BDR cluster.

It leverages consensus-driven quorum to determine the correct connection end-pointin a semi-exclusive manner to prevent unintended multi-node writes from anapplication. This reduces the potential for data conflicts.