(Linux only)

Veritas InfoScale supports application isolation in a CVM cluster through the creation of disk group sub-clusters. A disk group sub-cluster consists of a logical grouping of nodes that can selectively import or deport shared disk groups. The shared disk groups are not imported or deported on all nodes in the cluster as in the traditional CVM environment. This minimizes the impact of node failures or configuration changes on applications in the cluster.

You can enable the application isolation feature by setting the CVMDGSubClust attribute for the CVMCluster resource in the VCS configuration file. When the cluster restarts, the feature is enabled and shared disk groups are not auto-imported to all nodes in the cluster. The first node that imports the disk group forms a disk group sub-cluster and is elected as the disk group master for the sub-cluster. The remaining nodes in the cluster that import the shared disk group are treated as slaves. All disk group level operations run on the master node of the disk group sub-cluster. You can switch the master at any time for each disk group sub-cluster. A node can play the role of a master for a sub-cluster as well as that of a slave for another sub-cluster.

If a node loses connectivity to the SAN, the I/Os for that node are shipped to another node in the disk group sub-cluster just as in traditional CVM environments. If the disk group fails due to failed I/Os on all disks in the disk group, it is disabled and the nodes that share the disk group must deport and import the disk group again.

A node can belong to multiple disk group sub-clusters. Each disk group sub-cluster provides all the capabilities of a clustered Veritas Volume Manager environment, with the exception of some features.

The application isolation feature is supported with CVM protocol version 160 and above. It is disabled, by default, both after installation and upgrade.