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The Added Complexity of SAN Management
Placing storage onto a network integrates all these management requirements and also introduces new features that result from the synthesis of storage and networking. Device discovery, zoning, LUN mapping, alternate pathing and failover, centralized backup, third-party copy, HBA and fabric management, and virtualization of storage assets within SANs impose new management tasks that are non-existent in direct-attached storage solutions. While these SAN-specific capabilities give customers a powerful toolset for managing storage data, they also inject added complexity into storage administration.
SAN management is predicated on a myriad of functions that must necessarily interact if the SAN is to perform its mission. Each device must be configured to its specific requirements. HBA vendors, switch vendors, storage array vendors, and tape vendors each provide their own device managers that must be invoked at least once for initial configuration. LUNs must be created, ports enabled, and parameters set. Once each component is operational, relationships between them must be defined.
HBAs must be assigned to specific storage LUNs, switch ports or attached devices must be zoned, and interswitch links for failover or load balancing must be defined. High availability solutions require additional management to ensure that redundant links are operational, clustering software is properly configured, or disk-to-disk data replication requirements are properly met. For redundancy purposes, management, snapshots, backup scheduling, and hierarchical disk-to-disk-to-tape utilities each require additional manual configuration and monitoring. Auxiliary functions such as bill-back for storage utilization, security policies, and capacity planning may also be implemented.
On top of all these strata, storage virtualization must hide the underlying complexity of the SAN and its management, although in today's products the manual overhead of virtualization setup is even more labor-intensive than non-virtualized storage administration. For the past few years, management vendors have been struggling to integrate these diverse functions into a single platform, but with only partial success.