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3.4. Global Cluster Properties

When a cluster is created, or if you select a cluster to configure, a cluster-specific page is displayed. The page provides an interface for configuring cluster-wide properties and detailed properties. You can configure cluster-wide properties with the tabbed interface below the cluster name. The interface provides the following tabs: General, Fence, Multicast, and Quorum Partition. To configure the parameters in those tabs, follow the steps in this section. If you do not need to configure parameters in a tab, skip the step for that tab.
  1. General tab — This tab displays cluster name and provides an interface for configuring the configuration version and advanced cluster properties. The parameters are summarized as follows:
    • The Cluster Name text box displays the cluster name; it does not accept a cluster name change. You cannot change the cluster name. The only way to change the name of a Red Hat cluster is to create a new cluster configuration with the new name.
    • The Configuration Version value is set to 1 by default and is automatically incremented each time you modify your cluster configuration. However, if you need to set it to another value, you can specify it at the Configuration Version text box.
    • You can enter advanced cluster properties by clicking Show advanced cluster properties. Clicking Show advanced cluster properties reveals a list of advanced properties. You can click any advanced property for online help about the property.
    Enter the values required and click Apply for changes to take effect.
  2. Fence tab — This tab provides an interface for configuring these Fence Daemon Properties parameters: Post-Fail Delay and Post-Join Delay. The parameters are summarized as follows:
    • The Post-Fail Delay parameter is the number of seconds the fence daemon (fenced) waits before fencing a node (a member of the fence domain) after the node has failed. The Post-Fail Delay default value is 0. Its value may be varied to suit cluster and network performance.
    • The Post-Join Delay parameter is the number of seconds the fence daemon (fenced) waits before fencing a node after the node joins the fence domain. The Post-Join Delay default value is 3. A typical setting for Post-Join Delay is between 20 and 30 seconds, but can vary according to cluster and network performance.
    Enter values required and Click Apply for changes to take effect.

    Note

    For more information about Post-Join Delay and Post-Fail Delay, refer to the fenced(8) man page.
  3. Multicast tab — This tab provides an interface for configuring these Multicast Configuration parameters: Let cluster choose the multicast address and Specify the multicast address manually. The default setting is Let cluster choose the multicast address. If you need to use a specific multicast address, click Specify the multicast address manually, enter a multicast address into the text box, and click Apply for changes to take effect.
    If you do not specify a multicast address, the Red Hat Cluster software (specifically, cman, the Cluster Manager) creates one. It forms the upper 16 bits of the multicast address with 239.192 and forms the lower 16 bits based on the cluster ID.

    Note

    The cluster ID is a unique identifier that cman generates for each cluster. To view the cluster ID, run the cman_tool status command on a cluster node.
    If you do specify a multicast address, you should use the 239.192.x.x series that cman uses. Otherwise, using a multicast address outside that range may cause unpredictable results. For example, using 224.0.0.x (which is "All hosts on the network") may not be routed correctly, or even routed at all by some hardware.

    Note

    If you specify a multicast address, make sure that you check the configuration of routers that cluster packets pass through. Some routers may take a long time to learn addresses, seriously impacting cluster performance.
  4. Quorum Partition tab — This tab provides an interface for configuring these Quorum Partition Configuration parameters: Do not use a Quorum Partition, Use a Quorum Partition, Interval, Votes, TKO, Minimum Score, Device, Label, and Heuristics. The Do not use a Quorum Partition parameter is enabled by default. Table 3.1, “Quorum-Disk Parameters” describes the parameters. If you need to use a quorum disk, click Use a Quorum Partition, enter quorum disk parameters, click Apply, and restart the cluster for the changes to take effect.

    Important

    Quorum-disk parameters and heuristics depend on the site environment and the special requirements needed. To understand the use of quorum-disk parameters and heuristics, refer to the qdisk(5) man page. If you require assistance understanding and using quorum disk, contact an authorized Red Hat support representative.

    Note

    Clicking Apply on the Quorum Partition tab propagates changes to the cluster configuration file (/etc/cluster/cluster.conf) in each cluster node. However, for the quorum disk to operate, you must restart the cluster (refer to Section 4.1, “Starting, Stopping, and Deleting Clusters”).
Parameter Description
Do not use a Quorum Partition Disables quorum partition. Disables quorum-disk parameters in the Quorum Partition tab.
Use a Quorum Partition Enables quorum partition. Enables quorum-disk parameters in the Quorum Partition tab.
Interval The frequency of read/write cycles, in seconds.
Votes The number of votes the quorum daemon advertises to CMAN when it has a high enough score.
TKO The number of cycles a node must miss to be declared dead.
Minimum Score The minimum score for a node to be considered "alive". If omitted or set to 0, the default function, floor((n+1)/2), is used, where n is the sum of the heuristics scores. The Minimum Score value must never exceed the sum of the heuristic scores; otherwise, the quorum disk cannot be available.
Device The storage device the quorum daemon uses. The device must be the same on all nodes.
Label Specifies the quorum disk label created by the mkqdisk utility. If this field contains an entry, the label overrides the Device field. If this field is used, the quorum daemon reads /proc/partitions and checks for qdisk signatures on every block device found, comparing the label against the specified label. This is useful in configurations where the quorum device name differs among nodes.
Heuristics
Path to Program — The program used to determine if this heuristic is alive. This can be anything that can be executed by /bin/sh -c. A return value of 0 indicates success; anything else indicates failure. This field is required.
Interval — The frequency (in seconds) at which the heuristic is polled. The default interval for every heuristic is 2 seconds.
Score — The weight of this heuristic. Be careful when determining scores for heuristics. The default score for each heuristic is 1.
Apply Propagates the changes to the cluster configuration file (/etc/cluster/cluster.conf) in each cluster node.
Table 3.1. Quorum-Disk Parameters