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An overview of all of the tasks is shown in Figure 12-4. The tasks that TS7700 runs, the correlation of the tasks to the components that are involved, and tuning points that can be used to favor certain tasks over others are all described next. 

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In general, the tasks are the same for all models of the TS7700. For the TS7700D, the backend tasks are not applicable. 

All of these tasks share resources, especially the TS7700 Server processor, TVC, and physical tape drives that are attached to a TS7700T. Contention might occur for these resources when high workload demands are placed on the TS7700. To manage the use of shared resources, the TS7700 uses various resource management algorithms, which can have a significant affect on the level of performance that is achieved for a specific workload. 

In general, the administrative tasks (except premigration) have lower priority than host-related operations. In certain situations, the TS7700 grants higher priority to activities to solve a problem state, including the following scenarios: 

GLYPH<SM590000> Panic reclamation: The TS7700T detects that the number of empty physical volumes dropped below the minimum value, and reclaims must be done immediately to increase the count. 

GLYPH<SM590000> Cache fills with copy data: To protect from uncopied volumes being removed from cache, the TS7700T throttles data coming into the cache. For the TS7700T, this type of throttling occurs only to Host I/O that is related to the CPx partitions. Data that is written to CP0 is not throttled in this situation. 

For more information about tasks processing, see IBM Virtualization Engine TS7700 Series Best Practices - Understanding, Monitoring and Tuning the TS7700 Performance , WP101465. 

