Metro Mirror and Global Mirror relationships can exist simultaneously between clusters. 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 intercluster links.
Metro Mirror and Global Mirror relationships manage heavy workload 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. 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 Global Mirror relationships when the link tolerance threshold is exceeded. As a result, Global Mirror writes can suffer degraded performance if Metro Mirror relationships use most of the capability of the intercluster link.