If the system is already configured I would download and run a tool like IOMeter. There are way too many factors that weigh in to be able to say for sure how many IOPS the system will have. By running that tool it will break all that down for you. To get to that utility go to the link below. [URL] Please let me know if you have any issues running this utility.
We have an MD3220i with dual controllers and 16 900GB 10k SAS drives.   Is there a way to calculate our theoretical IOPs max?  I've read [URL] which shows a 18k IOPs.  But of course that's based on that exact config.  With fewer drives I imagine we'll support fewer IOPs.  We're moving off another storage device, so I know our current IOPs, and I want to make sure this new device will support it.  
Calculate IOPS max for our MD3220i 