Cisco Cisco MDS 9500 Series Supervisor-2 Module Libro blanco
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Large Core/Edge SAN Design
The core/edge SAN design in Figure 4 shows how it is possible to build a SAN for up to 1984 host ports and 256 storage ports with an end-to-end
oversubscription ratio of 7.75:1 with a pair of core switches and four edge switches.
Figure 4. 2240-Port Core/Edge SAN Design
In this design, the port bandwidth reservation feature is used to dedicate forwarding resources on edge switches for ISL connectivity from the edge
to the core. Host-facing ports remain in shared mode. With the 48-port linecards, each port group contains 12 front-panel ports. Because each Cisco
MDS 9513 contains 11 linecards, there are 44 port groups across the entire switch: 32 of these 12-port port groups use a single ISL connected to
the core, with the remaining 11 ports in the port group used for host connectivity. The 12 remaining 12-port port groups use all ports available for
host connectivity.
Each edge switch connects to each of two core switches using 16 ISLs, each operating with 4 Gbps dedicated forwarding resource. These 32 ISLs
are splayed across the entire chassis, but are configured to reside within two PortChannel bundles (one for each core switch). This results in two
64-Gbps logical ISLs, one to each of the two core switches. With each host-facing port operating at 2 Gbps, this results in an overall ratio of 992
Gbps (496 host ports at 2 Gbps) to 128 Gbps (two 16-port 4-Gbps PortChannels). Put another way, that is an oversubscription ratio of 7.75:1.
Each of the core switches is configured with five 12-port modules and six 24-port modules. This provides each core switch with:
•
60 non-over-subscribed ports at 4 Gbps (12-port modules)—Used for ISLs
•
144 non-over-subscribed ports at 2 Gbps (24-port modules)—128 ports used for storage, 4 ports used for ISLs, 12 unused