Sun recommends that you strive for as much separation and hardware redundancy as possible when connecting each cluster node to shared data storage. This approach provides the following advantages to your cluster:
The best assurance of high availability for your clustered application
Good failure isolation
Good maintenance robustness
Sun Cluster is usually layered on top of a volume manager, mirrored data with independent I/O paths, or a multipathed I/O link to a hardware RAID arrangement. Therefore, the cluster software does not expect a node ever to ever lose access to shared data. These redundant paths to storage ensure that the cluster can survive any single failure.
Sun Cluster does support certain configurations that use a single, dual-port HBA to provide the required two paths to the shared data. However, using a single, dual-port HBA for connecting to shared data increases the vulnerability of your cluster. If this single HBA fails and takes down both ports connected to the storage device, the node is unable to reach the stored data. How the cluster handles such a dual-port failure depends on several factors:
the cluster configuration
the volume manager configuration
the node on which the failure occurs
the state of the cluster when the failure occurs
If you choose one of these configurations for your cluster, you must understand that the supported configurations mitigate the risks to high availability and the other advantages. The supported configurations do not eliminate these previously mentioned risks.