Hitachi TrueCopy for IBM z/OS User and Reference Guide (T5211-96001, June 2007)

About TrueCopy for z/OS Operations 2-9
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Remote Copy Connections
The remote copy connections are the physical paths used by the TrueCopy for
z/OS MCUs to communicate with the TCz RCUs. The maximum number of
physical paths per logical CU is eight for fibre-channel. The MCUs and RCUs
are connected via fibre-channel interface cables.
When fibre-channel interface (single-mode longwave) connections are used,
two switches are required for distances greater than 10 km (6.2 miles), and
distances up to 30 km (18.6 miles) are supported. Long-distance solutions are
provided, based on user requirements and workload characteristics, using
approved channel extenders and communication lines (e.g., T1/T3/ATM).
The MCU-to-RCU remote copy configuration for TCz Asynchronous has
different requirements than the TCz Synchronous configuration, as follows:
• TrueCopy for z/OS Sync supports 1-to-n and n-to-1 remote copy connections
(n≤4). One MCU can be connected to as many as four RCUs, and one RCU can
be connected to as many as four MCUs (one MCU/RCU = one physical CU,
including all CUs). TCz supports the dynamic switching capability of the
ESCDs which is used to share the physical interface cables between the
components. The ESCDs can accommodate channel-to-MCU and channel-to-
RCU connections in addition to the remote copy connections.
• TrueCopy for z/OS Async supports 1-to-1 remote copy connections within the
same consistency group. The M-VOLs and R-VOLs of the pairs in a
consistency group must be located within one physical MCU and one physical
RCU. This configuration ensures backup integrity for data which is spread
across multiple volumes within one USP V (e.g., large databases).
Note: TrueCopy 1-to-n and n-to-1 configurations are valid for TrueCopy for
z/OS Async, as long as each consistency group does not span local or
remote storage systems.
• Fibre remote copy supports 1-to-1 remote copy connections. One USP V as
an MCU can be connected to only one USP V as an RCU via optical fibre
cables. For the CUs within one USP V, 1-to-4 and 4-to-1 remote copy
connections are supported.
• One MCU port (initiator port) can be connected to 64 RCU ports (RCU target
ports). One RCU port can be connected to 16 MCU ports. However, the
number of logical paths that can be specified does not depend on the number
of connectable RCU or MCU ports.
Note: Hitachi strongly recommends that you establish at least two
independent remote copy connections (one per cluster) between each MCU
and RCU to provide hardware redundancy for this critical communications
path.