While Sizing a VMware VDI Infrastructure, we need to take a lot of things into consideration. What is the number of total desktops that are going to be provisioned, how many desktops will be used concurrently, what's the IOPS requirement, What's the Bootstorm IOPS blah blah blah blah.
It takes a lot of calculations to complete the sizing and its a tedious work. After all we are humans, we are known for committing mistakes. Take for example you made a mistake at the beginning of the calculation and you didn't realize it. Imagine if you'll have to redo the whole thing. Even if you got through the whole process without committing mistakes and it turned out to be a good solution, what if another requirement comes for more users next time? More users = complex calculations. What would you do then?
Here's a tool developed by Andre Leibovici
It makes your life easy as it asks you every detail that's possible and should be considered while sizing a VDI Infrastructure.
Off course there's a Excel sheet that is available on the VMware Communities but i would recommend it only for initial sizing of the infrastructure as it "assumes" lot of things by default.
If you are a storage guy and you are more concerned about the performance of VDI and want to drill down to the IOPS level and see what kind of workloads are generated out of our infrastructure, you can check the link below which lets you work on the IOPS calculation part
Remember, the way a infrastructure works is not only determined by what products are being used but also the kind of designing that goes into building it.