Slony-I is an asynchronous
master-slave replication
Replication in computing involves sharing information so as to ensure consistency between redundant resources, such as software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware ...
system for the
PostgreSQL
PostgreSQL (, ), also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. It was originally named POSTGRES, referring to its origins as a successor to the In ...
DBMS, providing support for cascading and
failover
Failover is switching to a redundant or standby computer server, system, hardware component or network upon the failure or abnormal termination of the previously active application, server, system, hardware component, or network in a computer net ...
. Asynchronous means that when a
database transaction has been committed to the master server, it is not yet guaranteed to be available in slaves. Cascading means that replicas can be created (and updated) via other replicas, i.e. they needn't directly connect to the master.
Terminology
The name "slony" comes from the
Russian word "слоны" which means "
elephants".
This is a reference to the PostgreSQL elephant logo, as well as being a "tip of the hat" to Vadim Mikheev, who came up with some of the core ideas Slony-I uses to work. Note that there is a whole set of related terminology:
; slony
: is the plural word for elephants, and indicates that a cluster consists of multiple databases
; slon
: is the singular word for elephant; each replication node is managed by a program named "slon", which aggregate together into the aforementioned "cluster of elephants"
; slonik
: is the word for a "little elephant," and is the name of the program used to configure the cluster. In effect, the "little elephant" tells the cluster, "here's what you need to do!"
Unique features
Unlike many other replication solutions for PostgreSQL, Slony-I is not tied to any particular version of the database, which makes it possible to upgrade a database cluster one node at a time, without material downtime. (Version 2.0.0 requires PostgreSQL 8.3+, though)
See also
*
PostgreSQL
PostgreSQL (, ), also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. It was originally named POSTGRES, referring to its origins as a successor to the In ...
*
Replication (computer science)
References
:*
:*
External links
Slony-I official websiteSlony tutorial: How to Setup Slony-I Replication with Postgres Plus
Data synchronization
PostgreSQL
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