Slony-I
Encyclopedia
Slony-I is an asynchronous master-slave replication system for the PostgreSQL
DBMS, providing support for cascading and failover
. 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.
word слоны which stands for "elephant
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
slon
slonik
PostgreSQL
PostgreSQL, often simply Postgres, is an object-relational database management system available for many platforms including Linux, FreeBSD, Solaris, MS Windows and Mac OS X. It is released under the PostgreSQL License, which is an MIT-style license, and is thus free and open source software...
DBMS, providing support for cascading and failover
Failover
In computing, failover is automatic switching to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the previously active application, server, system, or network...
. Asynchronous means that when a database transaction
Database transaction
A transaction comprises a unit of work performed within a database management system against a database, and treated in a coherent and reliable way independent of other transactions...
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 RussianRussian language
Russian is a Slavic language used primarily in Russia, Belarus, Uzbekistan, Kazakhstan, Tajikistan and Kyrgyzstan. It is an unofficial but widely spoken language in Ukraine, Moldova, Latvia, Turkmenistan and Estonia and, to a lesser extent, the other countries that were once constituent republics...
word слоны which stands for "elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
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!"