When you open a System Monitor (Performance Monitor) log file, you may receive:
Data source 'Filename.xxx' is invalid. The log file contains fewer than two data samples.
System Monitor requires at least two data points to use as end points.
Probable causes of the error are:
1. You ran the for less than 15 - 30 seconds.
2. The log file is too small. It must be greater than 20KB-30KB. Decrease the logging interval.
3. The log file is corrupt.