Tiering means as much as gradation, subdivision into ranks or division into levels. The term tiering is used in storage technology for tiered storage. This involves assigning data to different categories and storing it on different storage media with the aim of reducing overall storage costs.
Tier hierarchy forms the basis for hierarchical storage management. The categories to which data is assigned are based on security needs, availability, frequency of data use, or other performance requirements. Files are usually assigned automatically according to corporate policies. Specific storage media are assigned to each tier level. The most important and most frequently used data is stored on the tier with the shortest access time, solid-state drives( SSD). This high-performance storage is the fastest and the most costly. This tier is Tier 0, which is suitable for ultra-high-speed applications, financial transactions, and fast e-commerce applications.
The next tier down is Tier 1, which uses primary storage, storage networks, and NAS storage and is reserved for less critical data. This tier supports fast reads and writes and is used for mission-critical applications. For example, data mining, business processing, and high-speed applications. The next tier down is Tier 2, which is for backup and recovery of data. Accordingly, hard disks with SATA interfaces and SAS interfaces are used on this tier. And the lowest tier is Tier 3 for archiving and long-term storage, for which LTO drives or other tertiary storage are typically used.