IT Storage world traditionally classifies storage disk based on its technology example SATA, SCSI, SSD, Fibre Channel etc. Your storage selection basically depends on the kind of read write requirement and budget. For Instance SSD is expensive but ideal for storing operating system files and file servers on the other hand need more capacity and tolerance so SATA is a good fit here. Server 2012 has a new feature which helps analyzing data based on its usage. This data is moved from a slow disks to SSD to improve performance.
With Windows Server 2012 storage spaces you can have two type of storage tiers, essentially a fast and a slow storage tier based on the connected disks or media type. The system performs this task automatically. Keep in mind that storage tier option gets enabled only when you have at least one SSD and a HDD in your storage pool. Screenshot below show the disabled option when you try to create a VHD from a storage pool.
The Storage tier management service performs a very crucial task of analyzing data on the disk in slices of 1MB. That is when the analogy of hot spots and cold spots come in picture. Spots are the area of data on the disk that are accessed frequently and cold spots are its exact opposite. After the analysis hot spots are promoted to SSD tiers and identified cold spots are allocated the regular HDD tiers. The analysis happens everyday at 1.00 AM. You can configure it to happen whenever you want by editing the storage tier optimization job under task scheduler – Microsoft\Windows\Storage Tier Management
The task basically runs a defrag command on the disk with “-g” parameter which optimizes the storage tiers. C and H parameters determine all volumes and normal priority on the task respectively.
It is also possible to pin a file to fast tier manually using a power shell command. Jose Barreto has explained this in one of his technet blogs.
Hope you find this useful.