Tiering refers to dividing the storage media in a cluster into different tiers based on performance differences, and assigning specific purposes to each. Typically, physical disks with higher performance and smaller capacity form the cache layer to handle direct user I/O operations, ensuring high throughput and low latency. Meanwhile, storage devices with relatively lower performance and larger capacity make up the capacity tier, used for long-term storage of user data. The storage system analyzes the frequency of data access and the utilization of space across different tiers, and automatically schedules data between the cache layer and the capacity tier.
