Hitachi G200 User Manual page 17

remote copy operations between various storage system models. This
document provides instructions for performing TrueCopy operations on
Hitachi Virtual Storage Platform G200, G400, G600, G800 (VSP G200,
G400, G600, G800) and Hitachi Virtual Storage Platform F400, F600,
F800 (VSP F400, F600, F800) primary storage systems.
• Main control units (MCUs) and remote control units (RCUs). The MCU is
the control unit in the primary storage system that controls the P-VOLs of
the TrueCopy pairs. The MCU communicates with the RCU through the
dedicated remote copy connections. The MCU controls the host I/O
operations to the P-VOLs as well as the TrueCopy remote copy operations
between the P-VOLs and S-VOLs. The MCU also manages the TrueCopy
pair status and configuration information.
The RCU is the control unit in the secondary storage system that controls
the S-VOLs of the TrueCopy pairs. The RCU assists in managing the
TrueCopy pair status and configuration (for example, rejects write I/Os to
S-VOLs). The RCU executes the remote copy operations issued by the
MCU. The RCUs should be attached to a host system to allow sense
information to be reported in case of a problem with a secondary volume
or remote storage system and to provide disaster recovery capabilities.
• Hosts. The hosts at the primary site are connected to the primary storage
system. Hosts at the secondary site are connected to the secondary
storage system for use in disaster recovery operations. If it is not possible
to have hosts at the secondary site, the host at the primary site must be
in communication with the secondary system.
• Volumes. The primary volumes (P-VOLs) on the primary storage system
are copied to the secondary volumes (S-VOLs) on the secondary system.
The P‑VOLs contain the original data, and the S‑VOLs are the mirrored
volumes that contain the backup or duplicate data. The primary and
secondary volumes must have the same format and capacity. During
normal TrueCopy operations, the P‑VOL remains available to all hosts at
all times for read and write I/O operations and the secondary storage
system rejects all host-requested write I/Os for the S‑VOLs. The S‑VOL
write enable option allows write access to an S‑VOL while the pair is split,
and the S‑VOL and P‑VOL differential data is used to resynchronize the
pair.
• Data paths. Dedicated data paths, also called remote copy connections,
are used for data transfer between the primary and secondary storage
systems. You should 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. The VSP Gx00
models and VSP Fx00 models support Fibre Channel and iSCSI remote
copy connections.
• Hitachi TrueCopy® software. The TrueCopy software must be installed on
both the primary and secondary storage systems and is used to perform
TrueCopy configuration and pair operations.
• CCI. The Command Control Interface (CCI) command-line interface
software can also be used for TrueCopy configuration and pair operations
as well as disaster recovery operations.
The following figure shows the TrueCopy system components.
Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
TrueCopy overview
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