1. A non-transitory computer-readable medium with instructions stored therein, the instructions, when executed by a processor, cause the processor to perform operations, the operations comprising: locking a first range of addresses corresponding to at least one data block on a composite data storage system; growing the range of locked addresses to a second range, the second range of addresses encompassing a migration unit of the at least one block on the composite data storage system; filling a data hole with a size of one or more migration units; and shrinking the range of locked addresses to the first range.