When upgrading to MySQL Enterprise Monitor 2.1 you should be aware of the following issues:
During the upgrade process, if you had previously set a Query Analyzer data purge value that was greater than the standard data purge value, the historical data collection purge period will be set to the Query Analyzer purge period. This will be logged in the upgrade log with the following notice:
getDataCollectionPurgeLifespan now: 4 weeks (was: 2 weeks)