According to one embodiment, a memory system includes a nonvolatile memory and a controller. The controller receives a first write request associated with first data from a host. In response to a lapse of first time since the reception of the first write request, the controller starts a write process of second data to the nonvolatile memory. The second data includes at least the first data. The controller transmits a first response to the first write request to the host in response to completion of the write process. The first time is time obtained by subtracting second time from third time designated by the host as a time limit of the transmission of the first response since the reception of the first write request.