Migrating data from a first storage device to a second storage device includes causing all data of the first storage device to be copied from the first storage device to the second storage device and causing the host computer to transition from performing I/O operations with the first storage device to performing I/O operations with the second storage device by modifying metadata used for I/O operations to change a mapping of logical devices to physical devices only after causing all data of the first storage device to be copied from the first storage device to the second storage device. Migrating data from the first storage device to the second storage device is independent of any I/O operations by the host. A data write operation from the host is acknowledged only after the data has been successfully written to both the first storage device and the second storage device.