Chapter 14. High Availability
Usage of XFS in conjunction with Red Hat Enterprise Linux 6.2 High Availability Add On as a file system resource is now fully supported.
Applications running inside VMWare based guests can now be configured for high availability. This also includes full support for the use of GFS2 shared storage file system in the environment. A new SOAP-based fence agent has been added that has the ability to fence guests when necessary.
Luci, the web-based administrative UI for configuring clusters has been updated to include the following:
- Role-based access control (RBAC): enables fine-grained access levels by defining user classes to access specific cluster operations.
- Improved response times for destructive operations in a cluster.
IP multicasting has been the only supported option for a cluster transport. IP multicasting is inherently complex to configure and often requires re-configuration of network switches. UDP-unicast in contrast offers a simpler approach to cluster configuration and is an established protocol for cluster communication. UDP-unicast, initially introduced as a Technology Preview, is now fully supported.
Watchdog is a general timer service available in Linux that can be used to periodically monitor system resources. Fence agents have now been integrated with watchdog such that the watchdog service can reboot a node after it has been fenced using
fence_scsi. This eliminates the need for manual intervention to reboot the node after it has been fenced using