Exchange 2013 released long back, but what was missing is Exchange role requirement & database calculators. The calculators helps in sizing the Exchange server role as well as plan the database storage design. People were waiting for the calculator as it helped in sizing and designing of the storage requirements. This was getting delayed and most awaited. The wait is over & Microsoft has released it Exchange 2013 server role as well as database sizing calculator.
The calculator can be downloaded from the below URL. More information about Exchange 2013 IO performance.
Exchange 2013 Server Role Requirements Calculator
Ask the Perf Guy: Sizing Exchange 2013 Deployments
Microsoft Exchange Server 2013 Management Pack