text: **Performance monitoring**
  
  This section highlights several performance monitoring techniques. 
  
  **Collecting performance statistics**
  
  IBM Spectrum Virtualize is constantly collecting performance statistics. The default frequency 
  by which files are created is 5-minute intervals. The collection interval can be changed by 
  using the**startstats**command. 
  
  The statistics files for volumes, managed disk (MDisks), nodes, and drives are saved at the 
  end of the sampling interval. A maximum of 16 files (each) are stored before they are overlaid 
  in a rotating log fashion. This design then provides statistics for the most recent 240-minute 
  period if the default 15-minute sampling interval is used. IBM Spectrum Virtualize supports 
  user-defined sampling intervals of 1 - 60 minutes. 
  
  For each type of object (volumes, MDisks, nodes, and drives), a separate file with statistic 
  data is created at the end of each sampling period and stored in /dumps/iostats. 
  
  Use the**startstats**command to start the collection of statistics, as shown in Example A-1. 
  
  Example A-1 The startstats command 
  
  IBM_Storwize:ITSO-V7k:superuser>startstats -interval 2 
  
  This command starts statistics collection and gathers data at 2-minute intervals. 