PerformancePoint Services could not connect to the specified data source. Verify that either the current user or Unattended Service Account has read permissions to the data source, depending on your security configuration. Also verify that all required connection information is provided and correct

Error: PerformancePoint Services could not connect to the specified data source. Verify that either the current user or Unattended Service Account has read permissions to the data source, depending on your security configuration. Also verify that all required connection information is provided and correct

Solution:
After spending lot time on this, we have resolved this.
The problem was, in our SharePoint farm, we are having 2 server. In one box, SQL Server 2008 r2 is not installed.

After installing SQL Server 2008 r2, our issue has fixed.