Configuring for high availability
This topic provides information that is needed to plan for a TS7700 Grid configuration to be used specifically for high availability.
The assumption is that continued access to data is critical and no
single point of failure, repair, or upgrade can be allowed to impact the availability of data. In a
high availability configuration, two or more TS7700 Clusters are in close proximity to one another
at the same site. The TS7700 Clusters are connected through a LAN. If one of the TS7700 Clusters
becomes unavailable because it has failed, is undergoing service, or is being updated, data can be
accessed through another TS7700 Cluster until the original TS7700 Cluster is again available. As
part of planning a TS7700 Grid
configuration to address this solution, you must consider the following:
- Plan for the virtual device addresses in the clusters to be configured to the local hosts. In this way, a total of 7681024 virtual tape devices (256 from each TS7700 Cluster) are available for use.
- Set up a copy consistency point of RUN for all data to be made highly available. With this copy consistency point, as each virtual volume is closed it is copied to the other another TS7700 Cluster.
- Design and code the data facility system managed storage (DFSMS) Automatic Class Selection routines to set the necessary copy consistency point.
- Design and code the DFSMS Automatic Class Selection routines to control what data gets copied and by which copy consistency point.
- Prepare procedures that your operators would execute if one of the TS7700 Clusters becomes unavailable. The primary task is to enable an ownership takeover mode against the a failed TS7700 Cluster to maintain continued access to data owned by the failed TS7700 Cluster.