Method and system for migrating data between flash memory devices

A storage controller, comprising:

• one or more processors;
• a host interface configured to couple the storage controller to a host;
• a storage medium interface configured to couple the storage controller to a storage medium including a plurality of flash memory devices, each with a plurality of flash memory blocks;
• and
• a storage controller memory storing instructions, which, when executed by the one or more processors, causes the storage controller to perform operations comprising:
• dividing each of the plurality of flash memory devices into a plurality of logical chunks, wherein each logical chunk includes one or more flash memory blocks;
• detecting failure of a number of flash memory blocks for a respective flash memory device of the plurality of flash memory devices, wherein each flash memory block is the minimum size erasable unit of a respective flash memory device in the plurality of flash memory devices;
• in accordance with a determination that the number of failed flash memory blocks satisfies a predefined threshold for the respective flash memory device, performing a migration process that includes:
• selecting one of the plurality of logical chunks of the respective flash memory device for migration in accordance with predefined selection criteria;
• and
• storing a replicated logical chunk, comprising a copy of the selected logical chunk, at a second flash memory device different from the respective flash memory device;
• remapping an address of the selected logical chunk to a physical location of the replicated logical chunk;
• and
• decreasing a number of logical chunks associated with the respective flash memory device, resulting in a reduced, non-zero number of logical chunks associated with the respective flash memory device;
• wherein, upon completion of the migration process, logical chunks of the plurality of logical chunks, other than the selected one, continue to be stored by the respective flash memory device.

A non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage controller coupled to a storage medium including a plurality of flash memory devices, wherein each flash memory device includes a plurality of flash memory blocks, the one or more programs including instructions that when executed by the one or more processors cause the storage controller to:

• divide each of the plurality of flash memory devices into a plurality of logical chunks, wherein each logical chunk includes one or more flash memory blocks;
• detect failure of a number of flash memory blocks for a respective flash memory device of the plurality of flash memory devices, wherein each flash memory block is the minimum size erasable unit of a respective flash memory device in the plurality of flash memory devices;
• in accordance with a determination that the number of failed flash memory blocks satisfies a predefined threshold for the respective flash memory device, performing a migration process that includes:
• selecting one of the plurality of logical chunks of the respective flash memory device for migration in accordance with predefined selection criteria;
• storing a replicated logical chunk, comprising a copy of the selected logical chunk, at a second flash memory device different from the respective flash memory device;
• remapping an address of the selected logical chunk to a physical location of the replicated logical chunk;
• and
• decreasing a number of logical chunks associated with the respective flash memory device, resulting a reduced, non-zero number of logical chunks associated with the respective flash memory device;
• wherein, upon completion of the migration process, logical chunks of the plurality of logical chunks, other than the selected one, continue to be stored by the respective flash memory device.