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Cisco is further down the road in offering fabric services in its MDS 9513 Multilayer Director SAN-OS, and on its Multiprotocol Services (MPS-18/4) and Storage Services Module (SSM) blades. (The SAN-OS term is commonly used across all Cisco FC switches and directors.
The directors from Brocade and Cisco are at different stages in their ability to help companies consolidate, control, and share their local and remote FC SAN resources (see "Key considerations to selecting a Fibre Channel director," PDF). For companies with highly distributed management environments that don't want central control, Brocade's architecture lets users introduce fabric services that preserve local administrative control while sharing SAN resources. Companies that need to centralize and standardize their FC infrastructure across the enterprise will be better served with Cisco's FC director architecture.
Consolidation and control
Consolidating remote SAN islands includes technical challenges and political issues about who will control the resources after the consolidation is complete. FC directors currently provide two methods to perform SAN consolidations: fabric mergers and fabric joins.
Brocade's 48000 Director and Cisco's MDS 9513 Multilayer Director allow companies to merge SAN islands into one large, logical fabric (see "Director FAQs"). But fabric mergers mean turning control over to one party--usually the department with the larger FC director. The merger also comes with countless technical intricacies. Verifying fabric settings and ensuring they're correct can exceed the time and risk thresholds of many companies. Rather than forcing companies to deal with these issues, Brocade and Cisco permit companies to join remote SAN islands to their large FC directors while keeping them logically separate. Users can share resources among virtual or logical SANs; if a tape drive or disk ports reside in one virtual SAN, servers in another virtual SAN can still access them.
That's where the similarities end. Cisco's virtual SAN (VSAN) technology is part of its native SAN-OS operating system found on its MDS 9500 Series Multilayer Directors. This permits FC switches, or directors of separate and potentially remote SAN islands, to connect to any FC port on the MDS 9500 and remain logically separate from other VSANs that exist on the MDS 9500. Brocade's logical SAN (LSAN) implementation is available only as part of its 48000 FR4-18i Director Blade or on its external 7500 SAN Router.
This was first published in August 2007