Calculating IOPS for EV 10.0.2

Hello,

I am planning a build of EV 10.0.2 for a customer that wants to archive about 500 to 600 mailboxes on a single Exchange 2010 database in a DAG configuration. I found the EV sizing calculator (called the ev 10 sizing estimator) which was useful for CPU and RAM needs (I will go with two servers - a SQL box and one EV server.) However, I was wondering if anyone has a method of estimating or calculating how many disk IOPS might be needed. I don't expect anyone to provide a hard estimate for my particular scenario, I am just asking how EV Architects normally tackle this question. Thanks!