According to one embodiment, in response to receiving a first namespace create command specifying a first attribution from a host, a controller creates a first namespace having the first attribution and a first logical address range. The first logical address range includes logical addresses. The controller sets each of the logical addresses to an unallocated state in which a physical address of the nonvolatile memory is not mapped, during a first period from a time when receiving a power loss advance notification or when detecting an unexpected power loss until a time when the controller becomes a ready state by resupply of a power to the memory system.