Configuring for both disaster recovery and high availability

It is possible to configure a TS7700 Grid to provide for both disaster recovery and high availability solutions. The assumption is that two or more TS7700 Clusters reside in different locations, separated by a distance dictated by your company's requirements for disaster recovery. In a three-cluster or four-cluster grid configuration, disaster recovery and high availability can also be achieved simultaneously by ensuring:

• Two local, high availability clusters possess RUN volume copies and have shared access to the host
• The third and fourth remote cluster possessesclusters possess deferred volume copies for disaster recovery

In addition to the considerations for configuring for disaster recovery, you must plan for:

• Access from your local site's hosts to the FICON® channels on the TS7700 Cluster at the disaster recovery site(s). This may involve connections that use dense wavelength-division multiplexing (DWDM) or channel extension equipment, depending on the distance that separates the sites. If the local TS7700 Cluster becomes unavailable, you would use this remote access to continue your operations by using a remote TS7700 Cluster.
• Differences in read or write performance as compared to the virtual devices on the local TS7700 Cluster. These can occur because the virtual devices on a remote TS7700 Cluster are connected to the host through channel extensions. If performance differences are a concern, when the local TS7700 is unavailable consider using only the virtual device addresses in a remote TS7700 Cluster. If performance differences are an important consideration, provide procedures both for ownership takeover and for an operator to vary the virtual devices in a remote TS7700 from online to offline.
• Creation of separate copy consistency policies for disaster recovery data and data that requires high availability.