The High Availability Add-On for Red Hat Enterprise Linux provides continuous availability of services by eliminating single points of failure. By offering failover services between nodes within a cluster, the High Availability Add-On supports high availability for up to 16 nodes. (Currently this capability is limited to a single LAN or datacenter located within one physical site.)| Features | Benefits |
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| Clustering |
Red Hat's High Availability Add-On enables applications to be highly available by reducing downtime and ensuring that there is no single point of failure in a cluster. It also isolates unresponsive applications and nodes so they can't corrupt critical enterprise data
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| Conga |
The Conga application of Red Hat Enterprise Linux provides centralized configuration and management for the High Availability Add-On
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| Corosync |
Corosync is a cluster executive within the High Availability Add-On that implements the Totem Single Ring Ordering and Membership Protocol, delivering an extremely mature, secure, high-performing, and lightweight high-availability solution
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| Integrated virtualization | Virtualization is pervasive throughout today's enterprise datacenters. Not only is Red Hat Enterprise Linux designed to be a superior guest on any of the major hypervisors, but it can also be a virtualization host. Virtualization is integrated directly into the Red Hat Enterprise Linux kernel using kernel-based virtual machine (KVM) technology. As part of the kernel, your administrators get the complete breadth of Red Hat Enterprise Linux system management and security tools and certifications |
| Fencing & unfencing |
Fencing is removing access to resources from a cluster node that has lost contact with the cluster, thereby protecting resources such as shared storage from uncoordinated modification.
Red Hat has made extensive improvements in the SCSI-3 PR reservations-based fencing. By enabling manual specification of keys and devices for registration and reservation, cluster administrators can bypass clvm and improve configuration and system flexibility.
After fencing, the unconnected cluster node would ordinarily need to be rebooted to safely rejoin the cluster. However, unfencing allows a node to re-enable access when starting up without administrative intervention.
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| Improved cluster configuration system |
The cluster configuration system now supports load options other than XML, including the Lightweight Directory Access Protocol (LDAP). Configuration reload is validated and easily synchronized across the cluster for better usability and manageability.
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| Virtualization integration |
You can now run virtualized KVM guests as managed services
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| Rich graphical user interface (GUI)-based cluster management and administration |
In Red Hat Enterprise Linux 6, the Web interface to luci has been redesigned and runs on TurboGears2
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| Unified logging and debugging |
System administrators can now enable, capture, and read cluster system logs via a single cluster configuration command
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