Hi Ed Sorry I have not responded in so long I have been dodging this project for far too long. Just to refresh I would like to state what I would like to achieve. 1. Performance Baseline of Exchange 2010 Mailbox Servers I plan to do this by installing all the relative Mailbox Counters in Perfmon.exe http://technet.microsoft.com/en-us/library/ff367871 What I dont know understand is how long I should run the perfmon counters for? and at what periods? will the perfmon logging cause significant distress to the server performance? All your advice and help is appreciated.