HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 102
Core-to-Edge Fabric, to scale through the addition of core elements. The topology offers
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Planning Considerations for Fibre Channel Topologies 3 A modified or partial-mesh fabric is similar to a full-mesh fabric, but each switch does not have to be directly connected to every other switch in the fabric. The fabric is still resilient to failure but does not carry a cost premium for unused or redundant ISLs. In addition, partial-mesh fabrics scale easier than full-mesh fabrics. Partial-mesh fabrics are useful when designing a SAN backbone for which traffic patterns between SAN islands connected to the backbone are well known. If heavy traffic is expected between a pair of switches, the switches are connected through at least one ISL; if minimal traffic is expected, the switches are not connected. In general, mesh fabrics can be difficult to scale without downtime. The addition of switches or directors usually involves disconnecting fabric devices and may involve disconnecting in-place ISLs. As a result, full or partial-mesh fabrics are recommended for networks that change infrequently or have well-established traffic patterns. Core-to-Edge Fabric A core-to-edge fabric consists of one or more directors or switches acting as core elements that are dedicated to connecting other directors and switches (edge elements) in the fabric. Core directors act as high-bandwidth routers with connectivity to edge fabric elements. Figure 3-10 illustrates the topology with two core directors and fourteen edge directors and switches (2-by-14 topology). Subject to large fabric design constraints, core-to-edge fabrics are easy to scale through the addition of core elements. The topology offers any-to-any device connectivity and evenly distributes traffic bandwidth throughout the fabric. The topology provides the most flexible architecture to address fabric performance, traffic locality, data integrity, connectivity, and scalability requirements. The simplest core-to edge fabric has two or more core switching elements that may or may not be connected (simple or complex). In a simple core topology as shown in Figure 3-10, core switches are not connected. In a complex core topology, core switches are connected. The figure also illustrates a topology where the core is a full-mesh fabric. 3-16 McDATA Products in a SAN Environment - Planning Manual