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340 IBM System Storage DS6000 Series: Copy Services with IBM System z
Figure 25-4 Remote storage disk subsystem with D volumes
You should still put the B and C volumes in different ranks. It is further recommended that you
configure corresponding B and C volumes in such a way that these volumes have an affinity
to the same server. It would also be ideal to have the B volumes connected to a different DA
pair than the C volumes.
25.5 Growth within Global Mirror configurations
When you add a rather large number of volumes at once to an existing Global Mirror session,
then the available resources for Global Copy within the affected ranks might be over-utilized
or even monopolized by the initial copy pass. To avoid too much impact, consider adding
many new volumes to an existing Global Mirror session in stages. If possible, and as a rough
rule of thumb, add only a few volumes in a rank during application peak I/O periods. After the
first initial copy is complete, add the next few volumes. Again, as a rule of thumb, plan for
adding one or two volumes in a rank during peak I/O load for the first initial copy pass. If
possible, then plan a massive add of new Global Copy volumes into an existing session
during off-peak periods.
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