A method of garbage collection for a storage medium in a storage device, the method comprising: determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks; determining a second trigger parameter in accordance with one or more operating conditions of a second sub-block of the first erase block in the storage medium; and characterized in that: in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block; and in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, enabling sub-block garbage collection of the second sub-block, wherein the first vulnerability criterion is distinct from the second vulnerability criterion, wherein the first vulnerability criterion is a first read-disturb threshold and the second vulnerability criterion is a second read-disturb threshold, distinct from the first read-disturb threshold, and wherein sub-block garbage collection of a particular sub-block of the first erase block is distinct from garbage collection of the first erase block, and sub-block garbage collection of the particular sub-block of the first erase block includes: writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and invalidating the particular sub-block in the first erase block. determining a first trigger parameter in accordance with one or more operating conditions of a first sub-block of a first erase block in the storage medium, the storage medium having a plurality of erase blocks that include the first erase block, where erase blocks are minimum size erasable units in the storage device and sub-blocks are sub-portions of corresponding erase blocks; determining a second trigger parameter in accordance with one or more operating conditions of a second sub-block of the first erase block in the storage medium; and characterized in that: in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block; and in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, enabling sub-block garbage collection of the second sub-block, wherein the first vulnerability criterion is distinct from the second vulnerability criterion, wherein the first vulnerability criterion is a first read-disturb threshold and the second vulnerability criterion is a second read-disturb threshold, distinct from the first read-disturb threshold, and wherein sub-block garbage collection of a particular sub-block of the first erase block is distinct from garbage collection of the first erase block, and sub-block garbage collection of the particular sub-block of the first erase block includes: writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and invalidating the particular sub-block in the first erase block. in accordance with a determination that the first trigger parameter meets a first vulnerability criterion, enabling sub-block garbage collection of the first sub-block; and in accordance with a determination that the second trigger parameter meets a second vulnerability criterion, enabling sub-block garbage collection of the second sub-block, wherein the first vulnerability criterion is distinct from the second vulnerability criterion, wherein the first vulnerability criterion is a first read-disturb threshold and the second vulnerability criterion is a second read-disturb threshold, distinct from the first read-disturb threshold, and wherein sub-block garbage collection of a particular sub-block of the first erase block is distinct from garbage collection of the first erase block, and sub-block garbage collection of the particular sub-block of the first erase block includes: writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and invalidating the particular sub-block in the first erase block. writing a copy of valid data from the particular sub-block to a second erase block in the storage medium, wherein the second erase block is distinct from the first erase block; and invalidating the particular sub-block in the first erase block.