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Chapter 3Service EnhancementsFor a summary of the service enhancements in the Foundation Services product, see the following sections: Introduction to Service EnhancementsA number of enhancements have been made to the Foundation Services to enable you to prioritize data integrity, to increase the availability of your applications, or to reduce disk and network load on the cluster. These enhancements are as follows:
Enable or disable these service enhancements to suit your cluster needs. Reduced Duration of Disk SynchronizationThis feature enables you to choose how the master and vice-master disks are synchronized. You can have synchronization either of an entire master disk or of only those blocks that contain data. By choosing the latter option, you reduce the time it takes to synchronize the master and vice-master disks. Set this feature to have the same value on both master-eligible nodes. If you change the value of the RNFS.SyncType property defining this feature, reboot the cluster as described in "Shutting Down and Restarting a Cluster" in the Netra High Availability Suite Foundation Services 2.1 6/03 Cluster Administration Guide. Choose the synchronization method by setting the value of the RNFS.SyncType parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, choose the synchronization method by setting the value of SLICE_SYNC_TYPE in the cluster_definition.conf file. For more information, see the nhfs.conf(4) and cluster_definition.conf(4) man pages. Data Management PolicyThere are three data management policies available in the current patch level of the Foundation Services 2.1 6/03. These policies determine how the cluster behaves when a failed vice-master reboots in a cluster that has no master node. The policy you choose depends on the availability and data-integrity requirements of your cluster. The data management policies are are the following:
Choose the data management policy by setting the value of the Cluster.DataManagementPolicy parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, choose the data management policy by setting the value of DATA_MGT_POLICY in the cluster_definition.conf file. For more information, see the nhfs.conf(4) and cluster_definition.conf(4) man pages. Masterless ClusterThis feature permits the diskless and dataless nodes to stay up even when there is no master node in the cluster. By default, this feature is disabled and so diskless and dataless nodes reboot if there is no master node in the cluster for more than a few minutes. Enable this feature if you want to reduce the possible downtime for services running on master-ineligible nodes. If you enable this feature, you must ensure that the diskless and dataless nodes can handle the situation where they would no longer be able to access the files exported by the master node. Activate this feature by setting the value of the CMM.Masterloss.Detection parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, enable this feature by setting the value of MASTER_LOSS_DETECTION in the cluster_definition.conf file. For more information, see the nhfs.conf(4) and cluster_definition.conf(4) man pages. Sanity Check of Replicated SlicesThis feature enables you to continuously scan the state of replicated slices. By default, this feature is disabled and it can only be used if the master and vice-master disks are synchronized. If you do not monitor the state of the replicated slices, it is possible that the vice-master disk is corrupted and so partly or completely inaccessible. Activate this feature by setting the value of the RNFS.CheckReplicatedSlices parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, enable this feature by setting the value of CHECK_REPLICATED_SLICES in the cluster_definition.conf file. For more information, see the nhfs.conf(4) and cluster_definition.conf(4) man pages. Delayed SynchronizationThis feature enables you to delay the start of synchronization between the master and vice-master disks. By default this feature is disabled. Delay synchronization if you do not want the synchronization task to conflict with other high CPU activities. If you enable this feature, you can trigger synchronization at a later time of your choosing using the nhenablesync command. Until synchronization is triggered and completed, the vice-master is not eligible to become master and so the cluster is open to a single point of failure. By delaying synchronization you are prolonging this vulnerability. Activate this feature by setting the value of the RNFS.EnableSync parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, specify the synchronization method by setting the value of SYNC_FLAG in the cluster_definition.conf file. For more information, see the nhfs.conf(4), cluster_definition.conf(4), and nhenablesync(1M) man pages. Serialized Slice SynchronizationThis feature enables you to synchronize the master and vice-master disks one slice at a time rather than all at once. By default this feature is disabled. Enabling this feature reduces the disk and network load. However, it limits the availability of the cluster during a certain limited time period because the vice-master cannot become master before all slices have been synchronized. During this time period, the cluster is vulnerable to a single point of failure. Activate this feature by setting the value of the RNFS.SerializeSync parameter in the nhfs.conf file. If you are installing the cluster with nhinstall, specify the synchronization method by setting the value of SERIALIZE_SYNC in the cluster_definition.conf file. For more information, see the nhfs.conf(4), and cluster_definition.conf(4) man pages. | ||||||||||||
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