Example Of A Cascaded Ficon Topology - HP XP20000/XP24000 Operation Manual

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
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.
In a Cascaded FICON topology, one Fibre Channel link is attached to the FICON channel. From the
switch, the FICON channel communicates with a number of FICON CUs on different switch ports. At
the control unit, the control unit and device-addressing capability is the same as the point-to-point
topology. However, communication and addressing capabilities are increased for the channel when
it is connected to a Fibre Channel switch, and can use the domain and port address portion of the
24-bit N_Port address to access multiple control units.
NOTE:
The domain address portion of the FC 24-bit port address is different because there are two Fibre
Channel switches in the channel-to-control unit path.
22 FICON/zHPF and ESCON host attachment
Figure 11. With this configuration, multiple channel