Chapter 3. Planning 75
For environments with higher bandwidth, non-cycling Global Mirror can be used so that less 
than a second of data is lost if a failure occurs. Global Mirror also works well when sites are 
more than 300 kilometers (186.4 miles) apart.
When Storwize V7000 copy services are used, all components in the SAN must sustain the 
workload that is generated by application hosts and the data replication workload. Otherwise, 
the system can automatically stop copy services relationships to protect your application 
hosts from increased response times. 
Starting with software version 7.6, you can use the chsystem command to set the maximum 
replication delay for the system. This value ensures that the single slow write operation does 
not affect the entire primary site.
You can configure this delay for all relationships or consistency groups that exist on the 
system by using the maxreplicationdelay parameter on the chsystem command. This value 
indicates the amount of time (in seconds) that a host write operation can be outstanding 
before replication is stopped for a relationship on the system. If the system detects a delay in 
replication on a particular relationship or consistency group, only that relationship or 
consistency group is stopped. 
In systems with many relationships, a single slow relationship can cause delays for the 
remaining relationships on the system. This setting isolates the potential relationship with 
delays so that you can investigate the cause of these issues. When the maximum replication 
delay is reached, the system generates an error message that identifies the relationship that 
exceeded the maximum replication delay.
To avoid such incidents, consider deploying a SAN performance monitoring tool, such as IBM 
Tivoli Storage Productivity Center, to continuously monitor the SAN components for error 
conditions and performance problems. The use of such tool helps you detect potential issues 
before they affect your environment.
When planning for use of the data replication services, consider the following aspects of the 
solution:
/SM590000Volumes and consistency groups for copy services
/SM590000Copy services topology
/SM590000Choice between Metro Mirror and Global Mirror
/SM590000Connection type between clusters (FC, FCoE, IP)
/SM590000Cluster configuration for copy services, including zoning
IBM explicitly tests products for interoperability with the Storwize V7000. For more information 
about the current list of supported devices, see the IBM System Storage Interoperation 
Center (SSIC) website.
Volumes and consistency groups
Determine whether volumes can be replicated independently. Some applications use multiple 
volumes and require order of writes to these volumes to be preserved in the remote site. 
Notable examples of such applications are databases. 
If application requires write order to be preserved for the set of volumes that it uses, create 
a consistency group for these volumes.