According to the Technet Physical Disk\Disk Transfers/sec counter over the peak 2 hours of server activity. Calculate your current IOPS/mailbox as described in the following formula: IOPS/mailbox = (average disk transfer/sec) (number of mailboxes) THen My question, after I get the IOPS/Mailbox, how do I know the bottomneck is the disk IO ? Thanks

You have not mentioned the Exchange version you are looking at but start with the notions containted here http://technet.microsoft.com/en-us/library/aa997558(EXCHG.65).aspx You want to look at the values of the disk latency in disk Transers /sec. Different versions of Exchange will have different recommend values, so you will need to make sure that you are looking at the right ones. I have to ask why you are asking this question- do you have a perf issue? Calculating IOPS per mailbox is meant to be done at the planning stage so you go out and buy the correctly sized disk units.Cheers, Rhoderick

I am using Exchange 2007, because most user using online mode and some user always complain performance issue. so I am checking what is the bottomneck? DC performace? Mailbox Server Disk IO and etc