IBM DS6000 Manual Do Utilizador

Chapter 13. Metro Mirror options and configuration 

Metro Mirror paths have certain architectural limits, as follows:

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A primary LSS can maintain paths to a maximum of four secondary LSSs. Each 
secondary LSS can reside in a separate DS6000.

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Up to eight logical paths per LSS-LSS relationship can be defined, and they will be defined 
over different physical links.

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An FCP port can host up to 2048 logical paths; these are the logical and directional paths 
that are made from LSS to LSS.

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An FCP link (the physical connection from one port to another port) can host up to 256 
logical paths.

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An FCP port can accommodate up to 126 different links (DS6000 port to DS6000 port 
through the SAN).

Prior to establishing your Metro Mirror solution, establish what your peak bandwidth 
requirement will be. This will help to ensure that you have enough Metro Mirror links in place 
to support that requirement. 

To avoid any response time issues, establish the peak write rate for your systems and ensure 
you have adequate bandwidth to cope with this load and allow for growth. Remember that 
only writes are mirrored across to the secondary volumes.

Tools to assist with this data collection include RMF™ in the z/OS environment.

For more information on bandwidth and available connection options, refer to IBM 
TotalStorage Business Continuity Solutions Guide, SG24-6547.

Because the DS6000 has made the LSS a topological construct, which is not tied to a 
physical array as in the ESS, the design of your LSS layout can be simplified. It is now 
possible to assign LSSs to applications, for example, without concern regarding 
under-allocation or over-allocation of physical disk subsystem resources. This can also 
simplify the Metro Mirror environment, because it is possible to reduce the number of 
commands that are required for data consistency.