Red Hat Cluster Suite
Encyclopedia
The Red Hat cluster suite includes software to create a high availability
and load balancing
cluster, it currently does not contain functionality for distributed computing. The cluster suite itself contains two products. Both can be used on the same system although this use case is unlikely. Both products have been initiated in the community and repackaged by Red Hat Enterprises. Computational clustering is not part of cluster suite, but instead provided by Red Hat MRG.
and services are able to be started.
The primary form of communicating node status is via a network device (commonly Ethernet
), although in the case of possible network failure, quorum can be decided through secondary methods such as shared storage
or multicast
.
Software services, filesystems 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 suite forcibly terminates a cluster node's access to services or resources to ensure the node and data is in a known state. The node is terminated by removing power
or access to the shared storage.
Service locking and control is guaranteed through fencing and STONITH
; more recent versions of Red Hat use a distributed lock manager (DLM)
, to allow fine grained locking and no single point of failure. Earlier versions of the cluster suite relied on GULM (grand unified lock manager) 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.
Virtual Machine .
as a filesystem in 3 and above. The load balancing software was a fork of the open source Piranha load balancing software.
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...
and load balancing
Load balancing (computing)
Load balancing is a computer networking methodology to distribute workload across multiple computers or a computer cluster, network links, central processing units, disk drives, or other resources, to achieve optimal resource utilization, maximize throughput, minimize response time, and avoid...
cluster, it currently does not contain functionality for distributed computing. The cluster suite itself contains two products. Both can be used on the same system although this use case is unlikely. Both products have been initiated in the community and repackaged by Red Hat Enterprises. Computational clustering is not part of cluster suite, but instead provided by Red Hat MRG.
High-availability cluster
A Red Hat cluster suite, when configured for high availability, 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 QuorateQuorum (Distributed Systems)
A quorum is the minimum number of votes that a distributed transaction has to obtain in order to be allowed to perform an operation in a distributed system...
and services are able to be started.
The primary form of communicating node status is via a network device (commonly Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
), although in the case of possible network failure, quorum can be decided through secondary methods such as shared storage
Storage area network
A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...
or multicast
Multicast
In computer networking, multicast is the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires...
.
Software services, filesystems 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 suite forcibly terminates a cluster node's access to services or resources to ensure the node and data is in a known state. The node is terminated by removing power
STONITH
STONITH , sometimes called STOMITH , is a technique for fencing in computer clusters. Fencing is the isolation of a failed node so that it does not cause disruption to a cluster...
or access to the shared storage.
Service locking and control is guaranteed through fencing and STONITH
STONITH
STONITH , sometimes called STOMITH , is a technique for fencing in computer clusters. Fencing is the isolation of a failed node so that it does not cause disruption to a cluster...
; more recent versions of Red Hat use a distributed lock manager (DLM)
Distributed lock manager
A distributed lock manager provides distributed software applications with a means to synchronize their accesses to shared resources....
, to allow fine grained locking and no single point of failure. Earlier versions of the cluster suite relied on GULM (grand unified lock manager) 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 on Red Hat Enterprise Linux 3 , 4 and 5)
- NFS (Unix) /CIFS (Windows)/GFS (Multiple Operating systems) File system failover support
- Service failover support
- Fully shared storage subsystem
- Comprehensive data integrity
- SCSI and fibre channel support
Load balancing cluster
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 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 VMwareVMware
VMware, Inc. is a company providing virtualization software founded in 1998 and based in Palo Alto, California, USA. The company was acquired by EMC Corporation in 2004, and operates as a separate software subsidiary ....
Virtual Machine .
History
The cluster suite is available in Red Hat Enterprise Linux 2.1, 3, 4 and 5. Supported Global File SystemGlobal File System
In computing, the Global File System is a shared disk file system for Linux computer clusters. This is not to be confused with the Google File System, a proprietary distributed filesystem developed by Google....
as a filesystem in 3 and above. The load balancing software was a fork of the open source Piranha load balancing software.