HP XP Continuous Access Software - Manual (Page 15)

Continuous Access XP user guide for the XP1024/XP128 15
Figure 2 Continuous Access XP components for Serial (ESCON) connections
XP1024/XP128
Continuous Access XP operations involve primary (main) disk arrays and secondary (remote) disk arrays
(MCUs and RCUs). This document describes Continuous Access XP operations in which the main disk
array is an XP1024/XP128 and the remote disk array is an XP1024/XP128. MCUs contain Continuous
Access XP primary volumes (P-VOLs), which contain original data and are online to the hosts. RCUs
contain Continuous Access XP secondary volumes (S-VOLs), which are synchronous or asynchronous
copies of the P-VOLs. Continuous Access XP supports all CU images and logical volumes of the disk array
and all physical hard drive options. Continuous Access XP supports RAID1 and RAID5 configurations for
the XP1024/XP128.
To provide greater flexibility and enable the disk array to be tailored to unique customer operating
requirements, additional operational parameters, or optional modes, are available for the disk array. At
installation, modes are set to their default values, so discuss these settings with your HP support team.
Modes can only be changed by your HP support team representative.
Contact your HP account support representative for the latest mode information.
Main and remote control units (MCUs and RCUs)
The main control unit (MCU) and remote control unit (RCU) control Continuous Access XP operations:
• The MCU is the control unit in the primary disk array that controls the P-VOLs of the Continuous Access
XP volume pairs. For Command View XP, the management station must be LAN-attached to the MCU
of each Continuous Access XP pair. For XP Remote Web Console and Command View XP, you need
connectivity between the arrays managed in the environment and the Web clients used to manage
them. The MCU communicates with the RCU via dedicated Fibre Channel remote copy connections.
The MCU controls host I/O operations to the Continuous Access XP P-VOLs and Continuous Access XP
initial copy and remote copy operations between the P-VOLs and S-VOLs. The MCU also manages
Continuous Access XP pair status and configuration information.
• The RCU is the CU in the remote disk array that controls the S-VOLs of the Continuous Access XP
volume pairs. The RCU assists in managing Continuous Access XP pair status and configuration (for
example, rejects write I/Os to Continuous Access XP S-VOLs). The RCU executes remote copy
operations issued by the MCU. For Command View XP, the management station must be
LAN-attached to the RCU of each Continuous Access XP pair. For XP Remote Web Console and
Command View XP, you need connectivity between the arrays managed in the environment and the
Web clients used to manage them. The RCUs should also be attached to a host system to allow sense