Abstract: A memory system includes a non-volatile memory including a first memory cell unit and a second memory cell unit, and a controller connectable to a host. The controller is configured to store an execution time of write and erase operations with respect to the first memory cell unit, receive from the host power-on time information indicating a power-on time of the memory system when the memory system is powered on, determine a first time period from a last write or erase operation with respect to the first memory cell unit based on the stored execution time and the power-on time, determine an execution time of a refresh operation of transferring data stored in the first memory cell unit to the second memory cell unit based on the first time period, and start the refresh operation at the determined execution time.

Abstract: According to one embodiment, a storage device includes a nonvolatile memory and a controller. The controller is configured to read data from the nonvolatile memory by applying a read voltage to the nonvolatile memory. The controller is configured to correct the read voltage based on a difference between a measured value of a bit number obtained when the data is read from the nonvolatile memory by applying the read voltage to the nonvolatile memory and an expected value of the bit number.

Abstract: According to one embodiment, a storage device includes a nonvolatile memory and a controller. The controller is configured to read data from the nonvolatile memory by applying a read voltage to the nonvolatile memory. The controller is configured to correct the read voltage based on a difference between a measured value of a bit number obtained when the data is read from the nonvolatile memory by applying the read voltage to the nonvolatile memory and an expected value of the bit number.