The present invention provides a server, including a casing; and at least one single server node of the server, disposed in the casing and comprising a hard disk of a first size, a drawout hard disk tray, a hard disk backplane, a mainboard and a node power distributing board, in which the hard disk of the first size is disposed on the drawout hard disk tray and at least two layers of the drawout hard disk trays are provided; each layer of the drawout hard disk tray is connected to the hard disk backplane via a retractable cable, or, each layer of the drawout hard disk tray is connected to the mainboard and the node power distributing board via the retractable cable, and the drawout hard disk tray is configured to perform a hot swap of the hard disk of the first size.