1. A computer system having a shared addressable memory space, comprising a data network for carrying data signals representative of computer readable information, and a plurality of computers, each of said plurality of computers sharing the shared addressable memory space and including an interface, coupled to said data network, for accessing said data network to exchange data signals therewith, a local volatile memory device coupled to said computer and having volatile storage for data signals, a local persistent memory device coupled to said computer and having persistent storage for data signals, and a shared memory subsystem for mapping a portion of said shared addressable memory space to a portion or the whole of said persistent storage and said volatile storage to provide thereby addressable persistent and volatile storage for data signals accessible by each of the plural computers, said shared memory subsystem including a distributor for mapping portions of said addressable memory space across said plurality of local persistent memory devices, to distribute said addressable memory space across said plurality of local persistent memory devices, and a disk directory manager for tracking said mapped portions of said addressable memory space to provide information representative of which of said local persistent memory devices has which of said portions of said addressable memory space mapped thereon.