McDATA Sphereon 4300 Specifications download pdf (Page 136)

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McDATA Products in a SAN Environment - Planning Manual

Planning Considerations for Fibre Channel Topologies

• Better fabric performance - As a connection between fabric

switches, a 10.2000 Gbps ISL delivers significantly greater

bandwidth. Fibre Channel devices that are not 10.2000 Gbps-

capable benefit from a higher-speed ISL, because slower traffic is

multiplexed and transmitted through the 10.2000 Gbps ISL.

• Additional port count - If additional ISL bandwidth is not

required for fabric performance, 10.2000 Gbps connectivity allows

the number of ISL connections to be reduced, thus yielding

additional director or switch ports for device connectivity.

When installing 10.2000 Gbps-capable fabric elements in a core-to-

edge topology, deploy the directors at the fabric core to provide

end-to-end high-speed ISL capability. If 10.2000 Gbps device

connectivity is required, attach the devices to the core director as Tier

1 devices. If possible, employ device locality by connecting 10.2000

Gbps devices to the same director.

FICON Cascading

The initial FICON architecture did not permit connection of multiple

directors or switches because the protocol specified a single byte for

the link (port) address definition in the input-output configuration

program (IOCP). The link address only defined the Port_ID for a

unique domain (director or switch).

The current FICON architecture provides two-byte addressing that

allows the IOCP to specify link (port) addresses for any number of

domains by including the domain address with the Port_ID. FICON

fabrics can now be configured using multiple directors and switches

(FICON cascading). In a cascaded FICON environment, at least three

Fibre Channel links are involved:

• The first link is between the FICON channel card (N_Port) of an

IBM eServer zSeries processor and a director or switch F_Port.

• The second link is an ISL between two director or switch E_Ports.

• The final link is from a director or switch F_Port to a FICON

adapter card (control unit N_Port) in a storage device, tape

device, or other peripheral.

These Fibre Channel links connect FICON fabric elements and

provide a physical transmission path between a channel and control

unit. Users may configure multiple ISLs between cascaded FICON

directors or switches to ensure redundancy and adequate bandwidth.

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McDATA Sphereon 4300 Specifications Page 136