Solid state memory (ssm), computer system including an ssm, and method of operating an ssm

Abstract

In one aspect, data is stored in a solid state memory which includes first and second memory layers. A first assessment is executed to determine whether received data is hot data or cold data. Received data which is assessed as hot data during the first assessment is stored in the first memory layer, and received data which is first assessed as cold data during the first assessment is stored in the second memory layer. Further, a second assessment is executed to determine whether the data stored in the first memory layer is hot data or cold data. Data which is then assessed as cold data during the second assessment is migrated from the first memory layer to the second memory layer.

What is claimed is: 
     
         1 . A memory system, comprising:
 a first group of memory cells, each of the first group of memory cells configured to store a first number of bits per cell;   a second group of memory cells, each of the second group of memory cells configured to store a second number of bits per cell; and   a controller configured to move data from the first group of memory cells to the second group of memory cells when the number of available memory cells in the first group of memory cell is less than a threshold,   wherein the first group of memory cells and the second group of memory cell are included in a first memory device.   
     
     
         2 . The memory system of  claim 1 , wherein the controller is configured to selectively move the data from the first group of memory cells to the second group of memory cells based on a write access frequency of the data. 
     
     
         3 . The memory system of  claim 1 , wherein the controller is configured to examine a write count value of each valid data in the first group of memory cells. 
     
     
         4 . The memory system of  claim 3 , wherein the controller is configured to classify the data based on the write count value of each valid data in the first group of memory cells. 
     
     
         5 . The memory system of  claim 1 , wherein the controller is configured to determine whether the number of the available memory cells in the first group of memory cells is less than the threshold. 
     
     
         6 . The memory system of  claim 5 , wherein the controller is configured to selectively move the data from the first group of memory cells to the second group of memory cells based on a write access frequency of the data. 
     
     
         7 . The memory system of  claim 1 , wherein the first group of memory cells are single-level flash memory cells, and the second group of memory cells are multi-level flash memory cells. 
     
     
         8 . The memory system of  claim 1 , wherein the first group of memory cells use a fine-grain mapping and the second group of memory cells use a coarse-grain mapping such that an operational speed of the first group of memory cells is faster than an operational speed of the second group of memory cells. 
     
     
         9 . The memory system of  claim 1 , wherein the controller is configured to move the data from the first group of memory cells to the second group of memory cells at periodic intervals when the number of available memory cells of the first group of memory cells is less than the threshold. 
     
     
         10 . The memory system of  claim 1 , wherein a first-type data is initially stored in the first group of memory cells and a second-type data is stored in the second group of memory cells, the first-type data having an access frequency that is greater than a predetermined access frequency, the second-type data having an access frequency that is lower than the predetermined access frequency. 
     
     
         11 . The memory system of  claim 10 , wherein the first-type data includes directory information and logging information, and
 the second-type data includes image files, sound files and program code.   
     
     
         12 . A method of managing data in a memory system that includes a first memory and a second memory, the method comprising:
 determining whether the number of available memory cells of the first memory is less than a threshold; and   moving data in the first memory to the second memory when the number of available memory cells of the first memory is less than the threshold.   
     
     
         13 . The method of  claim 12 , wherein the data is selectively moved from the first memory to the second memory based on a write access frequency of the data. 
     
     
         14 . The method of  claim 12 , wherein both the first memory and the second memory include multi-level memory cells, the number of bit per cell in the second memory being greater than the number of bit per cell in the first memory. 
     
     
         15 . The method of  claim 12 , wherein the first memory includes single-level memory cells, and the second memory includes multi-level memory cells. 
     
     
         16 . The method of  claim 12 , wherein the first memory and the second memory are a single integrated memory that is divided into a first group and a second group such that the first group is allocated as the first memory and the second group is allocated as the second memory. 
     
     
         17 . The method of  claim 12 , wherein a storage capacity of the second memory is greater than a storage capacity of the first memory. 
     
     
         18 . A method of managing data in a memory system comprising a first memory device that includes a first memory and a second memory, the method comprising:
 determining whether available memory cells of the first memory is greater than a first threshold; and   maintaining the available memory cells of the first memory above the threshold by moving to the second memory data that is stored in the first memory and has an access frequency lower than a second threshold,   wherein the first memory includes single-level memory cells, and the second memory includes multi-level memory cells.   
     
     
         19 . The method of  claim 18 , further comprising determining whether the second memory have available memory cells to receive the data from the first memory. 
     
     
         20 . The method of  claim 19 , wherein the data is moved from the first memory to the second memory only if the second memory is determined to have the available memory cells to receive the data from the first memory.