Metro Mirror and Global Mirror relationships can exist
simultaneously between systems. This type of configuration can affect 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 decreases.