HP XP P9500 Storage - Manual (Page 27)

Set port topology to the following:
NL/FL port: Fab on, FC-AL
F port: Fab on, Point-to-Point
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Best practice is to create at least two independent data paths (one per cluster) between the
primary and secondary systems for hardware redundancy for this critical element.
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When 4,000 pairs or more are used, we recommend that you restrict the number of pairs
when creating pairs, so that 4,000 pairs or less use one physical path, to distribute load on
the physical path.
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The same write-workload would be used in the reverse direction in a disaster recovery scenario.
Therefore, when planning Continuous Access Synchronous for disaster recovery, the same
number of secondary-to-primary data paths should be set up as the primary-to-secondary copy
paths for normal operations. Reverse direction paths must be set up independently of the
primary-to-secondary paths.
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When you set up secondary-to-primary data paths, specify the same combination of CUs or
CU Free—as were used for the primary-to-secondary paths.
Planning ports
Data is transferred along the data path from the initiator to RCU target ports on the primary and
secondary systems.
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Initiator ports send data.
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RCU target ports receive data.
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The amount of data each of these ports can transmit is limited.
You must know the amount of data that will be transferred (write-workload) during peak periods.
Then you can insure not only that bandwidth meets data transfer requirements, but that a sufficient
number of each system’s ports are specified as initiator and RCU target ports to handle all workload
levels.
The Fibre Channel ports on P9500 systems can have the following attributes:
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Target port: Connects the storage system and a host. When the host issues a write request,
the request is sent to a volume on the P9500 system via a target port on the storage system.
Target ports must be configured on the primary system for Continuous Access Synchronous
operations.
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Initiator port: Sends Continuous Access Synchronous commands to the paired storage system.
Initiator ports must be configured on the primary system for Continuous Access Synchronous
operations. When you want to copy data from secondary system to primary system, initiator
ports must be configured also on the secondary system.
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RCU Target port: Receives Continuous Access Synchronous commands and data. RCU target
ports must be configured on the secondary system for Continuous Access Synchronous
operations. When you want to copy data from secondary system to primary system, RCU
target ports must be configured also on the primary system.
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External port: Required for External Storage copy operations. This port is not used for
Continuous Access Synchronous copy operations. This port can be changed to a target,
initiator, or RCU target port.
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Initiator/external port: This setting shows the combination of ports that have an initiator port
and an external port attribute. Only a port that has an initiator port attribute within these ports
can be used for Continuous Access Synchronous. This attribute cannot be changed by the
Continuous Access Synchronous software. For details on the port to which an initiator/external
mix mode is set, see the HP P9000 External Storage for Open and Mainframe Systems User
Guide.
Planning data paths 27