Summary

Systems depend heavily on access to storage and data. When data access is stopped, systems stop working. Therefore, it's important to maintain data access. Connection redundancy improves data availability in SANs by creating multiple options for server-to-storage connections.

Hardware components such as HBAs, cables, and switches are often duplicated to allow uninterrupted operations following a component failure. SAN storage subsystems typically have multiple ports that can be used for redundant connections.

Dynamic multipathing software manages the processes of recognizing I/O transmission failures and failing over to a redundant path. The paths used by multipathing software are defined by the host initiator, the subsystem port/LUN combination, and the LU that processes storage commands for subsystem storage. As long as a host initiator can access the LU where data is stored, multipathing software should be able to maintain I/O operations.

Because multipathing is based on SCSI architectural elements, it is a very good idea to plan and use SCSI resources carefully, particularly watching the way LUNs are assigned to subsystem ports and LUs.