A data migration method, wherein the method comprises: obtaining, by a storage device, data access temperature of a first storage unit group (CKG 1, 30), wherein the first storage unit group (CKG 1, 30) comprises a plurality of storage units (grain 1, grain 2, 80), the storage units come from different disks of a same type, each storage unit (grain 1, grain 2, 80) is a composition unit of a block comprised in a logical unit, a logical unit block,, the logical unit is logical storage space that is provided by the storage device and accessible by a host, the data access temperature of the first storage unit group (CKG 1, 30) is determined based on data access temperature of each storage unit (grain 1, grain 2, 80), wherein the data access temperature of the first storage unit group is determined to be the sum of data access temperature of each storage unit, and the data access temperature of each storage unit (grain 1, grain 2, 80) is determined based on a data access temperature of a logical unit block in which the storage unit (grain 1, grain 2, 80) is located, wherein the data access temperature of each storage unit is determined as the data access temperature of a logical unit block in which the storage unit is located; and when the data access temperature of the first storage unit group (CKG 1, 30) reaches a specified threshold, migrating, by the storage device, data in the first storage unit group (CKG 1, 30) to a second storage unit group (CKG 2, 30), wherein access performance of the second storage unit group (CKG 2, 30) is higher than access performance of the first storage unit group (CKG 1, 30). obtaining, by a storage device, data access temperature of a first storage unit group (CKG 1, 30), wherein the first storage unit group (CKG 1, 30) comprises a plurality of storage units (grain 1, grain 2, 80), the storage units come from different disks of a same type, each storage unit (grain 1, grain 2, 80) is a composition unit of a block comprised in a logical unit, a logical unit block,, the logical unit is logical storage space that is provided by the storage device and accessible by a host, the data access temperature of the first storage unit group (CKG 1, 30) is determined based on data access temperature of each storage unit (grain 1, grain 2, 80), wherein the data access temperature of the first storage unit group is determined to be the sum of data access temperature of each storage unit, and the data access temperature of each storage unit (grain 1, grain 2, 80) is determined based on a data access temperature of a logical unit block in which the storage unit (grain 1, grain 2, 80) is located, wherein the data access temperature of each storage unit is determined as the data access temperature of a logical unit block in which the storage unit is located; and when the data access temperature of the first storage unit group (CKG 1, 30) reaches a specified threshold, migrating, by the storage device, data in the first storage unit group (CKG 1, 30) to a second storage unit group (CKG 2, 30), wherein access performance of the second storage unit group (CKG 2, 30) is higher than access performance of the first storage unit group (CKG 1, 30).