Q. With SSD getting cheaper is there any value to tiering storage anymore?
A. One of the great features in Windows Server 2012 R2 is tiering, which enables the storage in the Storage Space to be split into HDD and SSD tiers. This allows the most used blocks being moved to the SSD tier, while less used blocks being stored on HDDs.
I've had a number people ask why this is necessary with SSD prices decreasing however the reality is the SSD storage is still significantly more expensive per GB than HDD and for data that is not used as often spending money on SSD just to have the data not used does not make sense.
When you consider SSD, you are really paying for IOPS/$ while for HDD you are paying for GB/$. Therefore, tiering is critical to deliver a solution that is high performance (by moving the most used data to SSD for high IOPS) with high density (by having the less used data in HDD which has large amounts of space per $).
While one day the pricing for SSD may match HDD per GB, that is not the case today which means taking the best attributes of each types gives the best overall solution while optimizing your storage spend.