Remote Copy; Remote Copy Concepts - IBM V7000 Introduction And Implementation Manual

9.3 Remote Copy

In this section, we describe how the Remote Copy function works in IBM Flex System V7000
Storage Node. We also provide the implementation steps, using the GUI, for Remote Copy
configuration and management.
Remote Copy consists of three methods for copying: Metro Mirror, Global Mirror, and Global
Mirror with Change Volumes. Metro Mirror is designed for metropolitan distances with a
synchronous copy requirement. Global Mirror is designed for longer distances without
requiring the hosts to wait for the full round-trip delay of the long-distance link through
asynchronous methodology. From Version 6.4.1, Global Mirror with Change Volumes is an
added piece of functionality for Global Mirror designed to attain consistency on lower-quality
network links.
Metro Mirror and Global Mirror are IBM branded terms for the functions Synchronous Remote
Copy and Asynchronous Remote Copy. Throughout this book, the term "Remote Copy" is
used to refer to both functions where the text applies to each term equally.

9.3.1 Remote Copy concepts

In the Remote Copy, there are a number of different possible concepts that can be used when
performing the functions necessary to successfully reach your goal. In this section, we
describe these different concepts and the reasons for and results of their use.
Partnership
When creating a partnership, connect an IBM Flex System V7000 Storage Node to either
another IBM Flex System V7000 Storage Node, IBM Storwize V7000 systems or IBM SAN
Volume Controller (SVC) systems which are in separate clusters. These clusters can be
separated by distance, but distance is not a requirement. After the partnership creation has
been configured on both systems, further communication between the node canisters in each
of the storage systems is established and maintained by the SAN network. All inter-cluster
communication goes over either a Fibre Channel network or over an FCoE network.
Partnership must be defined on both storage systems to make the partnership fully functional.
Though partnerships for remote copy are created between the IBM virtual storage systems,
external storage system which are virtualized behind an IBM virtual storage system can be
used as members of the storage pools which have source or target volumes as members of a
remote mirrored pair. It does not mean that the external storage's mirroring product is
supported; but that the mdisk members can be accessed as storage members of the IBM
virtual storage system for use as virtual storage locations. This factor can impact the licensing
of the remote copy service on the IBM virtual storage systems.
A parameter named layer has been added to the clustered system properties which can be
changed from storage (default) to replication if you need to make a new relationship between
IBM Flex System V7000 Storage Node and an SVC system. You can only change this
parameter using the CLI command chsystem. In SVC systems, this parameter is fixed to
replication and cannot be changed.
Interconnection: Interconnects between an IBM Flex System V7000 Storage Node, an
IBM Storwize V7000, or an IBM SAN Volume Controller requires the use of Version 6.4.1
or later. Both systems in the partnership must be at the same level, and IBM Flex System
V7000 Storage Node must be set to the
replication. Usage limitations are described next in "Introduction to layers".
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IBM Flex System V7000 Storage Node Introduction and Implementation Guide
replication layer
using svctask chsystem -layer