HP Tru64 UNIX and TruCluster Server Version 5.1B-6

  Patch Summary and Release Notes > Appendix A Setting Up an Enhanced Distance Cluster   

Enhanced Distance Cluster Restrictions

Although an Enhanced Distance Cluster provides basic high availability between remote sites at greater distances, there are additional restrictions necessary to reduce the volume of data and its latency. Issues and restrictions are as follows:

  • The use of the Logical Storage Manager (LSM) to mirror user data or system disk/data in an Enhanced Distance Cluster configuration is prohibited. LSM can only be used for striping data in an Enhanced Distance Cluster.

  • Only single-instance applications are supported in an Enhanced Distance Cluster configuration. Multi-instance applications that use the cluster interconnect for communication between multiple instances, such as ORACLE RAC, are not recommended in a Enhanced Distance Cluster configuration. This is due to increased latency on the cluster interconnect. For example, ORACLE RAC uses a cluster interconnect for its own lock manager traffic and an increase in latency could lead to unpredictable results.

    Additionally, multi-instance applications can increase the burden on the cluster interconnect and affect inter-member cluster communication so should follow the configuration recommendations in the next section.

  • An Enhanced Distance Cluster should not be used for the following workloads due to their I/O characteristics and directory locations. (Mail and print usually keep their data stores in the system directories):

    • NFS server

    • Mail server

    • Print server