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5.4 New Functions
Among the many new functions that are included in Tivoli Storage Productivity Center for
Replication version 5.2, two of them address the management of new major functions in the
Storwize family. The following new major functions are described in the following sections:
򐂰 Global Mirror Failover/Failback with Change Volumes session
򐂰 Support for the SAN Volume Controller 6.4 option to move volumes between I/O groups
5.4.1 Global Mirror Failover/Failback with Change Volumes session
The Global Mirror Failover/Failback with Change Volumes session is available only for the
Storwize family of Storage Systems. It provides the same capabilities as the Global Mirror
Failover/Failback session type, but it also provides the option of enabling or disabling the use
of Change Volumes.
Change Volumes are composed of a source change volume and a target change volume that
contain a point-in-time image of the data from the source and target volumes. A FlashCopy
operation occurs between the source volume and the source change volume. The frequency
of the FlashCopy operation is determined by the cycle period. The data on the source change
volume is then replicated to the target volume, and finally to the target change volume.
Important: Do not confuse Change Volumes with FlashCopy target volumes or Practice
volumes. Change Volumes are dedicated to their respective SAN Volume Controller Global
Mirror sessions. Practice volumes are available for some session types in the DS8000
family.
Because the data that is replicated between sites contains point-in-time changes rather than
all changes, a lower bandwidth link is required between the sites. A regular Global Mirror
configuration requires the bandwidth between sites to meet the long-term peak I/O workload,
whereas Global Mirror with Change Volumes requires it to meet the average I/O workload
across a Cycle Period only. However, the use of change volumes can result in an increase to
your data exposure because it changes your Recovery Point Objective (RPO). Therefore, you
might want to include or exclude change volumes in your Global Mirror sessions, depending
on your network traffic or business requirements.
Note: One important feature of this kind of session is that you can monitor the current RPO
of your session. You can set two levels of thresholds, Warning and Severe, from 1 second
to 48 hours, and Tivoli Storage Productivity Center for Replication sends you an alert if
your remote copy session is no longer protecting your data for any reason with the RPO
you expect.
5.4.2 Support for the SAN Volume Controller 6.4 option to move volumes
between I/O groups
Tivoli Storage Productivity Center for Replication version 5.2 supports in its operations the
new option that is available in SAN Volume Controller code version 6.4 and higher to
non-disruptively migrate a volume to another I/O group. This is often done to manually
balance the workload across the nodes in a Storwize clustered system. A compressed
volume can also be moved, and you can specify the preferred node in the new I/O group.
Chapter 5. Tivoli Storage Productivity Center for Replication with SAN Volume Controller and Storwize family
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