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Chapter 15. Metro Mirror performance and scalability 183
15.2 Scalability
The DS6000 Metro Mirror environment can be scaled up or down as required. If new volumes
are added to the DS6000 that require mirroring, they can be dynamically added. If additional
Metro Mirror paths are required, they also can be dynamically added.
Remember that in the DS6000, you have only eight Fibre Channel ports available, four per
controller. Therefore, we recommend that you use two Fibre Channel links exclusively for
Metro Mirror, one on each controller, for availability.
If you need more bandwidth, you can increase the number of Metro Mirror links. It should be
symmetrical and it also depends on the controller used by the Extent Pool of your Metro
Mirror volumes.
We think that having no more than four exclusive Metro Mirror connections make sense. It is
the same as for your maximum host attachments at this time (unless you are using the
DS6000 mainly as a Metro Mirror target, with few or no host activities).
As previously mentioned, the logical nature of the LSS has made a Metro Mirror
implementation on the DS6000 easier to plan, implement and manage. However, if you need
to add more LSSs to your Metro Mirror environment, your management and automation
solutions should be set up to handle this.
The GDPS and eRCMF service offerings are designed to provide this functionality. Visit the
IBM Web site and see the Services & Industry Solutions page for more information. Also see
Part 8, “Solutions” on page 431.
Adding capacity to same DS6000
If you are adding capacity to an existing DS6000, providing your Metro Mirror link bandwidth
is not close to or over its limit, it is possible that you only have to add volume pairs to your
configuration. If you are adding more LSSs, then you must define Metro Mirror paths before
adding volume pairs.
Adding capacity in new DS6000s
If you are adding new DS6000s to your configuration, you must add physical Metro Mirror
links before defining your Metro Mirror paths and volume pairs. A minimum of two Metro
Mirror paths per DS6000 pair is recommended for redundancy reasons. Your bandwidth
analysis will indicate if you require more than two paths.