Multi-Target PPRC supports a local Metro Mirror pair and a remote Metro Global
Mirror pair configuration.
At the local h1 site, this configuration looks the same as having
only two Metro Mirror pairs. However, the recovery scenarios, after
a failure of site h1, are different because there is the Global Mirror
relationship from the h3 to h4 volumes to consider.
If a failure occurs at site h1, production can be swapped to either
the h2 or h3 site. A swap to h2 results in a Metro Global Mirror configuration
from the h2, h3, and h4 sites as shown in Figure 1. Figure 1. Multi-Target PPRC
configuration
A swap to h3 results in a Metro Mirror and Global Mirror configuration
with a Metro Mirror relationship between the h3 and h2 volumes and
a Global Mirror relationship between the h3 and h4 volumes.
Figure 2 shows a scenario
where h3 has three secondary volumes, h1, h2 and h4. Because h2 and
h4 are both active secondaries of h3, a set of Multi-Target Incremental
Resync pairs are created between even though there might not be any
intention of using them. Figure 2. Multi-Target PPRC
configuration
