To restrain a flutter of a magnetic disk in a high-speed hard disk drive, a ramp 40 is provided so as to be separated with a predetermined space from a side wall 12a of a base 12. The server compares an edge pair with an encrypted string value such that the encrypted string value is hidden from the client. The course can be repeated in 4-5 weeks. The width of a space between the guide sections is set so as to become greater than the width of each of the tongue-like flaps formed in the spring, and the rounded section is housed in the space between the guide sections. To ensure that each member is provided with the appropriate rate capacity, each member of the cluster runs an estimation algorithm to determine whether or not additional rate capacity should be reserved from the reservation coordinator, or released back into the cluster for redistribution.