Metro Mirror and Global Mirror relationships
can exist simultaneously between systems. In this type of configuration,
there can be impacts to performance because write data from both Metro Mirror and Global Mirror relationships
is transported over the same intersystem links.
Metro Mirror and
Global Mirror relationships
manage heavy workloads differently:
- Metro Mirror typically
maintains the relationships that are in the copying or synchronized
states, which causes the primary host applications to see degraded
performance.
- Noncycling Global Mirror requires
a higher level of write performance to primary host applications.
If the link performance is severely degraded, the link tolerance feature
automatically stops noncycling Global Mirror relationships
when the link tolerance threshold is exceeded. As a result, noncycling Global Mirror write
operations can suffer degraded performance if Metro Mirror relationships
use most of the capability of the intersystem link.
- Multiple-cycling Global Mirror relationships
do not degrade performance in heavy workload situations. Global Mirror relationships
instead allow the secondary volume to trail further behind the primary
volume until the workload has lessened.