1. In a storage subsystem that processes storage access commands received from a host system, a method of optimizing execution of storage access commands, the method comprising: receiving a calibration request from the host system, the request specifying a first write command and an optimization criterion; determining a speed of execution of the first write command, the determining comprising: using power provided by a primary power source, executing the first write command, and recording the execution speed of the first write command for each of a plurality of regions of a non-volatile memory storage device; selecting a region from the plurality of regions having a recorded execution speed that satisfies the optimization criterion; and when there is a failure of the primary power source, executing, using power provided by a reserve power source, a second write command directed to the selected region, wherein overhead operations that are directed to the selected region are disabled until the second write command has finished executing, the overhead operations comprising block erase, wear leveling, and bad block management operations.