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Chapter 3 # Service Enhancements For a summary of the service enhancements in the Foundation Services product, see the following sections: Introduction to Service Enhancements Reduced Duration of Disk Synchronization Data Management Policy Masterless Cluster Sanity Check of Replicated Slices Delayed Synchronization Serialized Slice Synchronization ## Introduction to Service Enhancements A 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:
Prioritizing data integrity | Reduced Duration of Disk Synchronization The `Integrity` and `Adaptability` data management policies, as described in Data Management Policy
Improving availability | The `Availability` data management policy, as described in Data Management Policy Masterless Cluster Delayed Synchronization
Reducing disk and network load | Serialized Slice Synchronization
Enable or disable these service enhancements to suit your cluster needs. ## Reduced Duration of Disk Synchronization This 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 Policy There 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:
`Integrity` | Ensures that the cluster uses the most up-to-date data. The vice-master does not take the master role but waits for the old master to return to the cluster. This is the default data management policy.
`Availability` | Prioritizes the availability of services running on the cluster over data integrity. The vice-master node takes the master role when there is no master in the cluster. This policy triggers a full synchronization when the old master node joins the cluster as the vice-master node. This synchronization might result in the loss of any data written to the old master while the vice-master was down.
`Adaptability` | Prioritizes availability only if the master and vice-master disks are synchronized. Such disk synchronization would increase the level of data integrity. The vice-master checks the disk synchronization state. If the state indicates that the master and vice-master nodes are not synchronized, the vice-master node does not take the master role but waits until the old master node returns to the cluster. If the state indicates that the master and vice-master disks are synchronized, the vice-master takes on the master role without waiting for the old master to rejoin the cluster.
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 Cluster This 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 Slices This 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 Synchronization This 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 Synchronization This 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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