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In this example, the maximum total data transfer value is 497 MBps (MiB/s Total Xfer), but that value is mainly driven by the premigration read task (MiB/s Fr_TVC PreMig). If premigration causes an performance issue, review the PMPRIOR and PMTHLVL setting for tuning. 

## Summary reports 

In addition to daily and monthly summary reports per cluster, VEHSTATS provides a side-by-side comparison of all clusters for the entire measurement interval. Examine this report for an overall view of the grid, and for significant or unexpected differences between the clusters. 

## 11.5.6 Performance evaluation tool for VEHSTATS reports 

After you collect the statistics data from your clusters, you can use available tools to format and plot the binary data. 

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

When evaluating performance, a graph that reveals a significant amount of information succinctly is the cache throughput  for a cluster graph. 

Performance tools are available on the IBM Techdocs website that take 24 hours of 15-minute VEHSTATS data, seven days of 1-hour VEHSTATS data, or 90 days of daily summary data and create a set of charts for you. 

The material does not contain any information about the specifics of a Tape Attach model. However, the other information is still valuable, and did not change, especially how to create the excel spreadsheet and the charts. 

See the following Techdocs sites for the performance tools, and the class replay for detailed information about how to use the performance tools: 

GLYPH<SM590000> Tools 

GLYPH<SM590000> Class replay 

The 24-hour, 15-minute data spreadsheets include the cache throughput chart. Figure 11-31 shows the cache throughput that was plotted from VEHSTATS. 

<img src='content_image/1014044.jpg'>

