are you ask SmartTier? if you ask SmartTier, A storage pool consists of one or more storage tiers. A maximum of three storage tiers are supported. The types of disks in a storage pool determine the allowed number of storage tiers. A storage pool housing one type of disks can only create a single storage tier, and cannot utilize the SmartTier to perform intelligent data storage. and if you want know more detail information,please check the follow link:
https://support.huawei.com/enterprise/en/doc/EDOC1000138877/6382c71/working-principle
