That is pretty much the same formula I use. Snapshots aren't available today, but when they would be I usually take 20% as the overhead instead of 15 to ensure you have some spare capacity for them. IOPS is difficult, it is a cloud and it should cater for different kind of workloads and they will be really divers. I would select a standard raid-level with a standard amount of disks that hits the sweet spots for your array. So for instance with NetApp RAID-DP is usually the best way to go.
Duncan
VMware Communities User Moderator | VCDX
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