Memory system

Abstract

According to one embodiment, a nonvolatile memory having memory blocks, and a controller configured to select a first block and a second block among the memory blocks, determine a third percentage on the basis of a first percentage of valid data in the first block and a second percentage of valid data in the second block, determine a first ratio between a write amount of user data in accordance with a request from a host and a write amount of the valid data into the first block on the basis of the third percentage, and write the user data and the valid data in the first block into the nonvolatile memory on the basis of the first ratio.

What is claimed is: 
     
         1 . A memory system comprising:
 a nonvolatile memory having memory blocks; and   a controller configured to:   select a first block and a second block among the memory blocks;   determine a third percentage on the basis of a first percentage of valid data in the first block and a second percentage of valid data in the second block;   determine a first ratio between a write amount of user data in accordance with a request from a host and a write amount of the valid data into the first block on the basis of the third percentage; and   write the user data and the valid data in the first block into the nonvolatile memory on the basis of the first ratio.