According to one embodiment, a memory system includes a nonvolatile memory including plural blocks each including plural pages, and a controller. When receiving a write request designating a first logical address and a first block number from the host, the controller determines a first location in a first block having the first block number to which data from the host should be written, and writes the data from the host to the first location in the first block. The controller notifies the host of either an in-block physical address indicative of the first location, or a group of the first logical address, the first block number and the first in-block physical address.