A study on the optimal control limit policy for inspections of hard disk sectors
Hiroyuki Hirakoshi, Hiroaki Sandoh, Toshio Nakagawa · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 1999
Presently, hard disks have become indispensable elements in most computer systems. If any malfunction occurs in the hard disk, valuable data can be lost; malfunctions such as sector failures can be caused by defects of the magnetic materials on the recording medium. When a sector failure occurs, the data in the failed sector are lost. However, the entire function can be restored to a normal condition by providing a process of replacement of the subject sector into a spare sector in advance. Since there is an upper limit to the number of spare sectors, a general failure can occur if the total number of sector failures exceeds the upper limit. Alternatively, an unstable state occurs in which the restoration of the information is not possible even though the entire structure appears to be working. It is rare that sector failure is discovered immediately. Instead, it is discovered when the hard disk is inspected. It is therefore possible to determine the total number of sector failures by periodic inspection and to avoid general failures and the extremely unstable states due to sector failure by preventive replacement. For the above situations, this paper proposes a control limit policy for the inspection of sector failure and verifies its effectiveness. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(10): 18–24, 1999