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Chapter 8. Clustering

Dynamic Token Timeout for Corosync

The token_coefficient option has been added to the Corosync Cluster Engine. The value of token_coefficient is used only when the nodelist section is specified and contains at least three nodes. In such a situation, the token timeout is computed as follows: 
[token + (amount of nodes - 2)] * token_coefficient
This allows the cluster to scale without manually changing the token timeout every time a new node is added. The default value is 650 milliseconds, but it can be set to 0, resulting in effective removal of this feature.
This feature allows Corosync to handle dynamic addition and removal of nodes.

Corosync Tie Breaker Enhancement

The auto_tie_breaker quorum feature of Corosync has been enhanced to provide options for more flexible configuration and modification of tie breaker nodes. Users can now select a list of nodes that will retain a quorum in case of an even cluster split, or choose that a quorum will be retained by the node with the lowest node ID or the highest node ID.

Enhancements for Red Hat High Availability

For the Red Hat Enterprise Linux 7.1 release, the Red Hat High Availability Add-On supports the following features. For information on these features, see the High Availability Add-On Reference manual.
  • The pcs resource cleanup command can now reset the resource status and failcount for all resources.
  • You can specify a lifetime parameter for the pcs resource move command to indicate a period of time that the resource constraint this command creates will remain in effect.
  • You can use the pcs acl command to set permissions for local users to allow read-only or read-write access to the cluster configuration by using access control lists (ACLs).
  • The pcs constraint command now supports the configuration of specific constraint options in addition to general resource options.
  • The pcs resource create command supports the disabled parameter to indicate that the resource being created is not started automatically.
  • The pcs cluster quorum unblock command prevents the cluster from waiting for all nodes when establishing a quorum.
  • You can configure resource group order with the before and after parameters of the pcs resource create command.
  • You can back up the cluster configuration in a tarball and restore the cluster configuration files on all nodes from backup with the backup and restore options of the pcs config command.