Why such an architecture?
Let's take a step back to understand the fundamental reason for the somewhat complex VSAN architecture. While the cost estimates may vary slightly from time to time, it will only proportionally vary.
An enterprise flash device cost per 10 GB is approximately $10, while the cost of a magnetic disk per 10 GB is approximately $1.
In contrast, from an Input/Output Operations Per Second (IOPS) perspective, the flash device costs $0.01 per IOPS and a magnetic disk costs $3.
It's not rocket science to realize that the capacity of a magnetic disk is fairly cheap and the cost of IOPS is exponentially cheaper for an SSD.
An architectural model that can leverage the IOPS capabilities of a flash device and storage capacity of the magnetic disk strikes an optimal balance with price and performance. This, of course coupled with the fact that we don't need the luxuries of a fabric infrastructure and a SAN array, means that this architecture exponentially optimizes the price and performance...
