HP Surestore 64 FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availabil - Page 89

Fabric Topologies, Cascaded Fabric

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Planning Considerations for Fibre Channel Topologies Fabric Topologies Several topologies exist from which to build a Fibre Channel fabric infrastructure. This section describes the most effective fabric topologies, and provides guidance on when to deploy each topology. The topologies are effective for a wide variety of applications, are extensively tested by HP, and are deployed in several customer environments. Fabric topologies described in this section include: ■ Cascaded. ■ Ring. ■ Mesh. ■ Core-to-edge. ■ Fabric islands. Cascaded Fabric A cascaded fabric consists of a linear string of directors or switches connected by one or more ISLs. Each fabric element is connected to the next fabric element in line. The end-point fabric elements are not connected to each other. Figure 36 illustrates a cascaded fabric topology. Cascaded fabrics are typically inexpensive, easy to deploy, and provide a simple solution to add additional fabric devices. However, this fabric design has low reliability because each director, switch, or ISL is a single point of failure. In addition, the design has limited scalability because the maximum hop count can be quickly exceeded when fabric elements are added. SAN High Availability Planning Guide 89

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Planning Considerations for Fibre Channel Topologies
89
SAN High Availability Planning Guide
Fabric Topologies
Several topologies exist from which to build a Fibre Channel fabric infrastructure.
This section describes the most effective fabric topologies, and provides guidance
on when to deploy each topology. The topologies are effective for a wide variety
of applications, are extensively tested by HP, and are deployed in several customer
environments.
Fabric topologies described in this section include:
Cascaded.
Ring.
Mesh.
Core-to-edge.
Fabric islands.
Cascaded Fabric
A cascaded fabric consists of a linear string of directors or switches connected by
one or more ISLs. Each fabric element is connected to the next fabric element in
line. The end-point fabric elements are not connected to each other.
Figure 36
illustrates a cascaded fabric topology.
Cascaded fabrics are typically inexpensive, easy to deploy, and provide a simple
solution to add additional fabric devices. However, this fabric design has low
reliability because each director, switch, or ISL is a single point of failure. In
addition, the design has limited scalability because the maximum hop count can
be quickly exceeded when fabric elements are added.