Storage device performing garbage collection and garbage collection method of storage device

A storage device comprising:

• at least one nonvolatile memory device including a plurality of memory blocks, the nonvolatile memory device configured to store user data and meta data in the plurality of memory blocks;
• and
• a device controller configured to control the nonvolatile memory device, the device controller including,
• at least one memory configured to store user cost information for each of the plurality of memory blocks, and to store meta cost information for each of the plurality of memory blocks, and
• processing circuitry configured to,
• calculate a user cost corresponding to a time of memory accesses to the user data during garbage collection within the plurality of memory blocks based on the user cost information based on at least (i) a time for reading one page of the user data and (ii) a time for programming one page of the user data,
• calculate a meta cost corresponding to a time of memory accesses to the meta data during the garbage collection within the plurality of memory blocks based on the meta cost information based on at least (i) a time for reading one page of the meta data and (ii) a time for programming one page of the meta data,
• calculate a garbage collection cost per free page of each of the plurality of memory blocks based on the user cost and the meta cost, and
• select one of the plurality of memory blocks having a lowest garbage collection cost per free page as a victim block,
• wherein the device controller is configured to calculate the garbage collection cost per free page of each of the plurality of memory blocks based on tGCCPP=(tUC+tMC)/(TPC−VPC), wherein
• tUC represents the user cost of each of the plurality of memory blocks, tMC represents the meta cost of each of the plurality of memory blocks, TPC represents a number of total pages of each memory block, VPC represents a number of valid pages of each memory block, and tGCCPP represents the garbage collection cost per free page.

A garbage collection method of a storage device, the storage device including at least one nonvolatile memory device including a plurality of memory blocks, the method comprising:

• calculating a user cost corresponding to a time of memory accesses to user data stored in the nonvolatile memory device during garbage collection within the plurality of memory blocks based on at least (i) a time for reading one page of the user data and (ii) a time for programming one page of the user data;
• calculating a meta cost corresponding to a time of memory accesses to meta data stored in the nonvolatile memory device during the garbage collection within the plurality of memory blocks based on at least (i) a time for reading one page of the meta data and (ii) a time for programming one page of the meta data;
• calculating a garbage collection cost per free page of each of the plurality of memory blocks based on the user cost and the meta cost;
• selecting one of the plurality of memory blocks having a lowest garbage collection cost per free page as a victim block;
• and
• performing the garbage collection on the victim block,
• wherein the garbage collection cost per free page of each of the plurality of memory blocks is calculated based on tGCCPP=(tUC+tMC)/(TPC−VPC), wherein
• tUC represents the user cost of each of the plurality of memory blocks, tMC represents the meta cost of each of the plurality of memory blocks, TPC represents a number of total pages of each memory block, VPC represents a number of valid pages of each memory block, and tGCCPP represents the garbage collection cost per free page.