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46 Chapter 2 Overview of CCI Operations
2.8.2 CCI Instance Configurations
The basic unit of the CCI software structure is the CCI instance. Each copy of CCI on a server
is a CCI instance. Each instance uses a defined configuration file to manage volume
relationships while maintaining awareness of the other CCI instances. Each CCI instance
normally resides on one server (one node). If two or more nodes are run on a single server
(e.g., for test operations), it is possible to activate two or more instances using instance
numbers. The CCI command, Hitachi TrueCopy or ShadowImage, is selected by the
environment variable (HORCC_MRCF). The default command execution environment for CCI
is Hitachi TrueCopy.
The CCI instance shown in Figure 2.21 has a remote execution link and a connection to the
RAID storage
system. The remote execution link is a network connection to another PC to
allow you to execute CCI functions remotely. The connection between the CCI instance and
the storage system illustrates the connection between the CCI software on the host and the
command device. The command device accepts TrueCopy and ShadowImage CCI commands
and communicates read and write I/Os between the host and the volumes on the storage
system. The host does not communicate Hitachi TrueCopy or ShadowImage commands
directly to the volumes on the storage system. The CCI commands always go through the
command device.