In modern storage devices (especially All Flash Arrays), extensive data reduction techniques are commonplace and expected by customers.
This has, unavoidably, led to various marketing schemes that aim to make certain systems seem more appealing than the rest. Or at least not less appealing…
I will attempt to explain what customers should be looking for when trying to decipher capacity claims from a manufacturer.
In a nutshell – and for the ADD-afflicted – the most important number you should be looking for is the Effective Capacity Ratio, which is simply: (Effective Capacity)/(Raw Capacity). Ignore the more common but far less useful Data Reduction Ratio, which is: (Effective Capacity)/(Usable Capacity).