1. A method of managing a command queue within a storage device defining a multiplicity of block addresses for storing user data blocks and receiving into the command queue a group of presently unexecuted input/output (I/O) commands for the device from a host system, the method comprising the steps: maintaining a sequential ordering of said group of commands within the command queue; maintaining command execution dependency relation information for each command of said group, each dependency relation indicating an overlap of block addresses between a given command and other commands within the group; identifying a set of independent commands within the group as having no block address overlap relative to other commands within the group; and selecting one of said independent commands for promotion to a command execution position within the command queue, said selected independent command determined by the device to be a least-latent one of said independent commands relative to a head-of-queue command presently being executed within the storage device.