Slony-I

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.

Terminology

The name "slony" comes from the Russian word "слоны" which means "elephants".[1] 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)

gollark: (somehow I wrote microUSB there, oops)
gollark: I'm comparing it to USB-A for point 4.
gollark: <@!111608748027445248> - Too many different things over identical looking physical connectors: a "USB-C" port might support power-delivery *input*, power-delivery *output*, Thunderbolt, two different incompatible kinds of video output, and various speeds from USB 2.0 to USB 3.2 Gen2x2 (whyyy).- The ports on devices can end up wearing out problematically, though I don't know if this is better or worse than on competitors like Lightning or µUSB.- A lot of peripherals still don't support it, though this is hardly *its* fault.- I think the smaller connector means you can't put as much weight on it safely, for bigger USB stick-y devices, though I am not sure about this.
gollark: Eh. Sort of. It has its own problems.
gollark: Also, it's USB-C, so you'll need a cable for that.

See also

References
  1. "Slony-I 2.2.5 Documentation: Slony-I Concepts". 2016-05-31. Retrieved 2017-02-02.


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