Slony-I is an asynchronous
master-slave replication system for the
PostgreSQL
PostgreSQL ( ) also known as Postgres, is a free and open-source software, free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. PostgreSQL features transaction processing, transactions ...
DBMS, providing support for cascading and
failover. Asynchronous means that when a
database transaction
A database transaction symbolizes a unit of work, performed within a database management system (or similar system) against a database, that is treated in a coherent and reliable way independent of other transactions. A transaction generally rep ...
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 "
elephant
Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s".
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 software, free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. PostgreSQL features transaction processing, transactions ...
*
Replication (computer science)
Replication in computing refers to maintaining multiple copies of data, processes, or resources to ensure consistency across redundant components. This fundamental technique spans database management system, databases, file system, file systems, a ...
References
:*
:*
External links
Slony-I official websiteSlony tutorial: How to Setup Slony-I Replication with Postgres Plus
Data synchronization
PostgreSQL
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