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Chapter 13. Metro Mirror options and configuration 145
Figure 13-7 Logical paths for Metro Mirror
Metro Mirror paths have certain architectural limits, as follows:
A primary LSS can maintain paths to a maximum of four secondary LSSs. Each
secondary LSS can reside in a separate DS6000.
Up to eight logical paths per LSS-LSS relationship can be defined, and they will be defined
over different physical links.
An FCP port can host up to 2048 logical paths; these are the logical and directional paths
that are made from LSS to LSS.
An FCP link (the physical connection from one port to another port) can host up to 256
logical paths.
An FCP port can accommodate up to 126 different links (DS6000 port to DS6000 port
through the SAN).
13.5 Bandwidth
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.
13.6 LSS design
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.
DS6000 1
Port
1 logical path
LSS 2
LSS 3
LSS 1
1 logical path
1 logical path
Port
1 logical path
LSS 2
LSS 3
LSS 1
1 logical path
1 logical path
3-9 logical paths
1 Link
Metro Mirror
paths
DS6000 2
switch