Nonvolatile data storage systems, methods, and devices are disclosed. In one example, a nonvolatile storage device includes a volatile memory, a controller electrically coupled to the volatile memory, a nonvolatile memory electrically coupled to the controller, and a backup power source electrically coupled to the controller, the volatile memory, and the nonvolatile memory. The controller is configured to read and write primary data from a primary host and mirrored data from a secondary host in the volatile memory. The backup power source is configured to store sufficient energy to power the nonvolatile storage device during a backup operation. The controller is configured to, in response to a backup signal, copy the primary data and the mirrored data stored in the volatile memory to the nonvolatile memory.