Cascaded Ficon Topology - HP XP P9500 Operation Manual

Figure 9 Example of a switched point-to-point topology

Cascaded FICON topology

A FICON channel in FICON native (FC) mode connects one or more processor images to a Fibre
Channel link, which connects to a Fibre Channel switch, and then dynamically through one or
more FC switch ports (internally within the switch) to a second FC switch in a remote site via FC
link(s). From the second FC switch port, a number of Fibre Channel links connect to FICON CU
ports, which interconnect with one or more control units and/or images (logical control units). This
forms a cascaded FICON topology (see the following figure). The cascaded FICON directors
topology is only supported by IBM zSeries processors.
Figure 10 Example of a cascaded FICON topology
In a cascaded FICON topology, one or two switches reside at the topmost (root) level, between
the channel (CHL) and disk controller (DKC) ports (see
multiple channel images and multiple control unit images can share the resources of the Fibre
Channel link and Fibre Channel switches, so that multiplexed I/O operations can be performed.
Channels and control unit links can be attached to the Fibre Channel switches in any combination,
depending on configuration requirements and Fibre Channel switch resources.
Sharing a control unit through a Fibre Channel switch allows communication between a number
of channels and the control unit to occur either:
Over one switch-to-CU link, such as when a control unit has only one link to the Fibre Channel
switch, or
Over multiple-link interfaces, such as when a control unit has more than one link to the Fibre
Channel switch.
16 FICON/zHPF host attachment
Figure 1 1 (page 17). With this configuration,