The Red Hat Cluster includes software to create a

high availability High availability (HA) is a characteristic of a system which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period. Modernization has resulted in an increased reliance on these systems. Fo ...

and load balancing cluster. Both can be used on the same system although this use case is unlikely. Both products, the High Availability Add-On and Load Balancer Add-On, are based on

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

community projects. Red Hat Cluster developers contribute code upstream for the community. Computational clustering is not part of cluster suite, but instead provided by Red Hat MRG.

High-Availability Add-On

The High Availability Add-On is Red Hat's implementation of

Linux-HA The Linux-HA (High-Availability Linux) project provides a high-availability ( clustering) solution for Linux, FreeBSD, OpenBSD, Solaris and Mac OS X which promotes reliability, availability, and serviceability (RAS).Alan Robertson ''The Evolu ...

. It attempts to ensure service availability by monitoring other nodes of the cluster. All nodes of the cluster must agree on their configuration and shared services state before the cluster is considered to have a

quorum A quorum is the minimum number of members of a deliberative assembly (a body that uses parliamentary procedure, such as a legislature) necessary to conduct the business of that group. According to ''Robert's Rules of Order Newly Revised'', the ...

and services are able to be started. The primary form of communicating node status is via a network device (commonly

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

), although in the case of possible network failure, quorum can be decided through secondary methods such as shared storage or

multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...

. Software services,

filesystem In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

s and network status can be monitored and controlled by the cluster suite, services and resources can be failed over to other network nodes in case of failure. The Cluster forcibly terminates a cluster node's access to services or resources, via fencing, to ensure the node and data is in a known state. The node is terminated by removing power (known as STONITH) or access to the shared storage. More recent versions of Red Hat use a

distributed lock manager Operating systems use lock managers to organise and serialise the access to resources. A distributed lock manager (DLM) runs in every machine in a cluster, with an identical copy of a cluster-wide lock database. In this way a DLM provides software ...

, to allow fine grained locking and no single point of failure. Earlier versions of the cluster suite relied on a "grand unified lock manager" (GULM) which could be clustered, but still presented a point of failure if the nodes acting as GULM servers were to fail. GULM was last available in Red Hat Cluster Suite 4.

Technical details

* Support for up to 128 nodes (16 nodes on Red Hat Enterprise Linux 3, 4, 5, and 6) * NFS (Unix) /SMB /GFS /GFS2 (Multiple Operating systems) File system failover support * Service failover support * Fully shared storage subsystem * Comprehensive data integrity * SCSI and fibre channel support * OCF and LSM resource agents

Load Balancing Add-On

Red Hat adapted the Piranha load balancing software to allow for transparent load balancing and failover between servers. The application being balanced does not require special configuration to be balanced, instead a Red Hat Enterprise Linux server with the load balancer configured, intercepts and routes traffic based on metrics/rules set on the load balancer.

Support and Product Life-Cycle

Red Hat cluster suite support is tied to a matching version of

Red Hat Enterprise Linux Red Hat Enterprise Linux (RHEL) is a commercial open-source Linux distribution developed by Red Hat for the commercial market. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop version ...

and follows the same maintenance policy. The product has no activation, time limit or remote kill switch, it will remain working after the support life cycle has ended. It is partially supported running under

VMware VMware, Inc. is an American cloud computing and virtualization technology company with headquarters in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture. VMware's desktop software ru ...

Virtual Machine.

History

The cluster suite is available in: *

2.1 * Red Hat Enterprise Linux 3.x, 4.x, 5.x - with supported

Global File System In computing, the Global File System 2 or GFS2 is a shared-disk file system for Linux computer clusters. GFS2 allows all members of a cluster to have direct concurrent access to the same shared block storage, in contrast to distributed file sys ...

(v1.x) as a filesystem * Red Hat Enterprise Linux 5 ** Red Hat Enterprise Linux 5.3 and later - with Global File System 2 * Red Hat Enterprise Linux 6.0 and later, with

Corosync (project) The Corosync Cluster Engine is an Open-source software, open source implementation of the Totem Protocol, Totem Single Ring Ordering and Membership protocol. It was originally derived from the OpenAIS project and licensed under the new BSD Licens ...

, CMAN, and RGManager ** Red Hat Enterprise Linux 6.5 and later, with

, CMAN, and RGManager, or Pacemaker Resource Manager * Red Hat Enterprise Linux 7.0 and later , with

and Pacemaker Resource Manager

References

External links

Red Hat Cluster Suite Red Hat Enterprise MRG
{{Red Hat Cluster computing High-availability cluster computing Red Hat software Virtualization software for Linux