IBM TS7700 Series Grid Resiliency Improvements User's Guide V1.1

Abstract

The IBM TS7700 Series is the latest in the line of tape virtualization products that has revolutionized the way mainframe customers run system z tape operations. A TS7700 Grid is made up of two or more TS7700 clusters interconnected through Ethernet connections and it is designed and implemented as a business continuance solution with implied enterprise resiliency. When a cluster in the Grid has a problem, the multi-cluster Grid should accommodate the outage and have the ability to continue the operation even if the state of the Grid is degraded.Some customers have experienced grid-wide problems that are due to a single cluster in the Grid experiencing a problem. That cluster could be considered sick or unhealthy, but not completely dead (Sick But Not Dead (SBND)). This can negatively affect performance of the entire grid, with customer jobs being affected (long mount time, failed sync mode writes… much more than degraded).Grid Resiliency Improvements, introduced in R4.1.2, are the functions to identify the symptoms of a SBND cluster and make the Grid more resilient removing the sick or unhealthy cluster from the Grid, either explicitly or implicitly through different methods.