Linux-HA
Encyclopedia
The Linux-HA project provides a high-availability
(clustering) solution for Linux
, FreeBSD
, OpenBSD
, Solaris and Mac OS X
which promotes reliability, availability
, and serviceability
(RAS).
The project's main software product is Heartbeat, a GPL
-licensed portable cluster management program for high-availability cluster
ing. Its most important features are:
Eventually Harald Milz wrote an odd sort of Linux-HA HOWTO. Unlike
most HOWTOs, this was not about how to configure or use existing software, it was
a collection of HA techniques which one could use if one were to write HA software for Linux.
Alan Robertson was inspired by this description and thought that he could perhaps write some of the
software for the project to act as a sort of initial seed crystal to help jump start the project.
He got this initial software running on 18 March, 1998. He created the first web site for the project on 19 October, 1998,
and the first version of the software was released on
15 November, 1998.
The first production customer of the software was Rudy Pawul of ISO-NE. The ISO-NE web site
went into production in the second half of 1999.
At this point, the project was limited to two nodes and very simple takeover semantics, and
no resource monitoring.
This was cured with version 2 of the software, which added n-node clusters, resource monitoring,
dependencies, and policies. Version 2.0.0 came out in 29 July, 2005.
This release represented another important milestone as it was the first version where very large contributions
(in terms of code size) were made by the Linux-HA community at large.
This series of releases brought the project to a level of feature parity-or-superiority
with respect to commercial HA software.
After version 2.1.4, the cluster resource manager component (responsible for starting and stopping resources and monitoring resource and node failure) was split off into a separate project called Pacemakerhttp://clusterlabs.org/wiki/Project_History, and the resource agents and other "glue" infrastructure were moved to separate packages. Thus with the version 3 series, the name Heartbeat should be used for the cluster messaging layer only.http://linux-ha.org/wiki/Heartbeat#Historical_note
High-availability cluster
High-availability clusters are groups of computers that support server applications that can be reliably utilized with a minimum of down-time. They operate by harnessing redundant computers in groups or clusters that provide continued service when system components fail...
(clustering) solution for Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, OpenBSD
OpenBSD
OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...
, Solaris and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
which promotes reliability, availability
Availability
In telecommunications and reliability theory, the term availability has the following meanings:* The degree to which a system, subsystem, or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time...
, and serviceability
Serviceability (computer)
In software engineering and hardware engineering, serviceability is one of the -ilities or aspects...
(RAS).
The project's main software product is Heartbeat, a GPL
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
-licensed portable cluster management program for high-availability cluster
High-availability cluster
High-availability clusters are groups of computers that support server applications that can be reliably utilized with a minimum of down-time. They operate by harnessing redundant computers in groups or clusters that provide continued service when system components fail...
ing. Its most important features are:
- no fixed maximum number of nodes - Heartbeat can be used to build large clusters as well as very simple ones
- resource monitoring: resources can be automatically restarted or moved to another node on failure
- fencing mechanism to remove failed nodes from the cluster
- sophisticated policy-based resource management, resource inter-dependencies and constraints
- time-based rules allow for different policies depending on time
- several resource scripts (for ApacheApache HTTP ServerThe Apache HTTP Server, commonly referred to as Apache , is web server software notable for playing a key role in the initial growth of the World Wide Web. In 2009 it became the first web server software to surpass the 100 million website milestone...
, DB2IBM DB2The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...
, OracleOracle databaseThe Oracle Database is an object-relational database management system produced and marketed by Oracle Corporation....
, PostgreSQLPostgreSQLPostgreSQL, 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...
etc.) included - GUIGraphical user interfaceIn computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
for configuring, controlling and monitoring resources and nodes
History
The project originated from a mailing list started in November 1997.Eventually Harald Milz wrote an odd sort of Linux-HA HOWTO. Unlike
most HOWTOs, this was not about how to configure or use existing software, it was
a collection of HA techniques which one could use if one were to write HA software for Linux.
Alan Robertson was inspired by this description and thought that he could perhaps write some of the
software for the project to act as a sort of initial seed crystal to help jump start the project.
He got this initial software running on 18 March, 1998. He created the first web site for the project on 19 October, 1998,
and the first version of the software was released on
15 November, 1998.
The first production customer of the software was Rudy Pawul of ISO-NE. The ISO-NE web site
went into production in the second half of 1999.
At this point, the project was limited to two nodes and very simple takeover semantics, and
no resource monitoring.
This was cured with version 2 of the software, which added n-node clusters, resource monitoring,
dependencies, and policies. Version 2.0.0 came out in 29 July, 2005.
This release represented another important milestone as it was the first version where very large contributions
(in terms of code size) were made by the Linux-HA community at large.
This series of releases brought the project to a level of feature parity-or-superiority
with respect to commercial HA software.
After version 2.1.4, the cluster resource manager component (responsible for starting and stopping resources and monitoring resource and node failure) was split off into a separate project called Pacemakerhttp://clusterlabs.org/wiki/Project_History, and the resource agents and other "glue" infrastructure were moved to separate packages. Thus with the version 3 series, the name Heartbeat should be used for the cluster messaging layer only.http://linux-ha.org/wiki/Heartbeat#Historical_note