A data storage system wherein each one of first directormemory boards includes a director coupled to a host computerserver; and a local cache memory section in communication with the director on such board. The DTE sends a second command to the DCE at an arbitrary timing upon reception of the first command. One of the blades treated as a pair is made of super-hard alloy and the other blade is made of one kind of material selected from the group of sintered ceramic, cermet, and microcrystalline diamond sintered material. They are prepared by impregnating polyolefin pellets in suspension in a pressure vessel with the blowing agent, cooling the batch below 100 C.