HP XP P9500 Storage - Manual (Page 39)

Planning ports for data transfer
Updated data is transferred along the data path from the initiator and RCU target ports on the
primary and secondary systems.
•
Initiator ports control the specific data link they are part of.
•
RCU target ports respond to commands from Initiator ports.
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The amount of data a port can transmit is limited.
Continuous Access Journal transfers data from the primary to the secondary storage system when
the secondary storage subsystem requests data. Hence, the data path to size for normal operations
is the path composed of links that have their Initiator ports in the secondary storage system and
their RCU target ports in the primary storage subsystem.
You must know the amount of data that will be transferred during peak periods. Then your need
to ensure that a sufficient number of your systems’ ports are specified as initiator and RCU target
ports to handle the potential amount of data.
The Fibre Channel ports on P9500 systems can have the following attributes:
•
Target port: Connects the storage system and an open systems 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 are not used with mainframe volumes or Continuous Access
Journal operations. This port can be changed to an initiator, or RCU target port.
•
Initiator port: Sends Continuous Access Journal commands to the paired storage system.
initiator ports must be configured on both primary and remote storage systems for Continuous
Access Journal operations.
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RCU Target port: Receives Continuous Access Journal commands and data. RCU target ports
must be configured on both primary and remote storage systems for Continuous Access Journal
operations.
•
External port: Required for External Storage copy operations. This port is not used for
Continuous Access Journal copy operations. This port can be changed to a target, initiator,
or RCU target port.
NOTE: One or more initiator ports must be configured on both the primary and secondary storage
subsystems before you can add the secondary storage system and create Continuous Access Journal
volume pairs. A minimum of two initiator ports on both the primary and secondary storage
subsystems (configured on separate fibre channel CHAs) is highly recommended for redundancy.
Determining required number of ports
The primary and secondary systems require both initiator and RCU target ports. Both systems send
and receive traffic during active replication.
•
The initiator port on the primary side is connected to the RCU target port on the secondary
side. These links carry status and command information during normal operation (e.g. copying
data from the primary to the secondary storage subsystem).
•
The initiator port on the secondary side is connected to the RCU target port on the primary
side. These links carry the data traffic during normal operation and must be sized for the
required capacity.
Adding more ports increases the amount of data that can be transferred between systems.
To determine the required number of initiator and RCU target ports
The data transfer speed of your Continuous Access Journal Z ports must be greater than peak write
IOPS. This means that you must dedicate the number of ports to a Continuous Access Journal Z
pair that will be able to handle the peak IOPS generated by your production system. The minimum
Planning ports for data transfer 39