Earlier the method of computing lies near CPU . CPU is the thing which drive,control,keeps and manage all the processing power. Although other peripherals too has processing power but that is driven by CPU or CPU utilize them according to needs of the event. One more thing lacks here is absences of cooirdination between these devices. So if the CPU fails the whole system becomes unavailable and overall a big loss of data,time and power etc. Here one more thing countable,if the CPU is not programmed to use the peak performance of these peripherals then there is also waste of processing power, That is why a need generated for such a system in which if there is a failure accured at the main core (grid) , then the control is transferred to a similar grid and system not affected by any thing. One more thing also present here which correlates this grids and keep updation. Because there are several grids and they are connected with each other and exchanging the latest information means whatever the event happen only required processing power given for the event.