HP XP20000/XP24000 HP StorageWorks XP Disk Array Mainframe Host Attachment and - Page 21

Cascaded FICON topology, Channel link, which connects to a Fibre Channel switch

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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 FICON switched point-to-point 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. The communication path between a channel and a control unit consists of the physical channel path and the logical path. In a FICON switched point-to-point topology with a single switch, the physical paths are the Fibre Channel links (interconnection of two Fibre Channel links connected by a Fibre Channel switch) that provide the physical transmission path between a channel and a control unit. 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. XP Disk Array Mainframe Host Attachment and Operations Guide 21

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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 FICON switched point-to-point 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.
The communication path between a channel and a control unit consists of the physical channel path
and the logical path. In a FICON switched point-to-point topology with a single switch, the physical
paths are the Fibre Channel links (interconnection of two Fibre Channel links connected by a Fibre
Channel switch) that provide the physical transmission path between a channel and a control unit.
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.
XP Disk Array Mainframe Host Attachment and Operations Guide
21