JPH0224877A - Magnetic disk controller - Google Patents

Abstract

PURPOSE:To reduce the head moving time by providing substituting tracks at the central part of a magnetic disk in the radial direction. CONSTITUTION:When a magnetic head accesses a defective track 2a, a controller identifies the defective track and moves the head to the central N/2 track of previously assigned substitute tracks 3. When a plural number of such defective tracks 2a exist, the controller controls the substitute tracks 3 to be assigned to the magnetic head in such a way that the N/2+1 track and N/2-1 track can be alternately accessed by the head after the N/2 track. When such constitution is used, the moving distance of the magnetic head from the defective track 2a to the substitute tracks 3 can be reduced as compared with the conventional example and the readout time of the head can be reduced. When the N is an odd number, the substitute track 3 to be accessed first can be st to (N+1)/2 or (N-1)/2 and the other substitute tracks 3 can be fixed alternately on both sides of the central track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk control device that is located between a host computer and a magnetic disk device and controls the magnetic disk device.

[Conventional technology]

One of the major causes of errors in reading recorded data recorded on tracks of a magnetic disk is errors caused by scratches or defects on the disk medium.

Since such errors often occur on that track, in actual use, the track is not used as a defective track, and instead an alternative track is assigned.

FIG. 2 is a diagram showing allocated areas of tracks on a magnetic disk in this type of conventional magnetic disk control device.

In the figure, (1) is a magnetic disk, and tracks for recording information are formed concentrically with a 0 track on the outermost circumference and an N track on the innermost circumference. Of these, the track from the outermost 0 track to the N-m-1) rack is the user-used track (2), and the track from the N-m trunk to the N-1 track is the alternative track (3). This is reserved in advance to replace the defective track (2a) when the user-used track (2) has a defective disk medium.

The innermost N track is a defect list track (4) in which the contents of corresponding commands for the defective track (2a) and an alternative track (3) to replace it are recorded.

FIG. 3 shows the above in addresses, with the cylinder address shown in the radial direction of the magnetic disk (1) and the head address shown in the axial direction taking into account a plurality of magnetic disks and magnetic heads.

Next, the operation will be explained. The magnetic head is driven and controlled in the radial direction of the magnetic disk (1) to read recorded data from a commanded user track (2). In this case, if the accessed track corresponds to the defective track (2a), an alternative track (3) specified in advance is selected and accessed by a command from the defect list track (4), and when the reading is completed, the next The user continues accessing the track (2) used by the user.

[Problem to be solved by the invention]

Since the conventional magnetic disk control device is configured as described above, the alternative track (3) is arranged on the inner circumference of the magnetic disk (1), and in particular, the defective track (2a) is located on the magnetic disk (1). 1 magnetic head moves from the defective track (2a) to the substitute track (2a) on the inner circumference.
3), which has the problem of increasing the maximum reading time of recorded data.

The present invention has been made to solve the above-mentioned problems, and provides a magnetic disk control device in which the maximum reading time of recorded data is shortened.

[Means to solve the problem]

In the magnetic disk control device according to the present invention, an alternative track is arranged at the radial center of the magnetic disk.

[Effect]

In this invention, when the magnetic head accesses a defective track, it moves to a designated alternative track, but since the alternative track is located at the center of the magnetic disk in the radial direction, the moving distance and therefore the maximum moving time are is reduced.

〔Example〕

FIG. 1 is a diagram showing allocated areas of tracks of a magnetic disk of a magnetic disk control device in an embodiment of the present invention. The difference between the figure and the conventional one shown in FIG. 2 is that an alternative track (3) is arranged at the radial center of the magnetic disk (1). That is, the alternative is the center track of N rack (3) or the i track. As a result, the track used by the user (2) is divided into an outer circumferential portion G2υ and an inner circumferential portion (2).

Next, the operation will be explained. When the magnetic head accesses the defective track (2a), the control device identifies the track as a defective track and moves the magnetic head to the center hook of the pre-assigned alternative track (3).

If there are a plurality of defective tracks (2a), control is performed to sequentially access alternative tracks (3) that are alternately allocated in the inner and outer circumferential directions centering on the i-track in the order of the first track.

By controlling as described above, the defective track (2a
) to the alternative track (3) is shorter than before, and the maximum reading time of recorded data is significantly reduced.

Note that in the above embodiment, the NN to the alternative track (3)
N Nm Tsukusu, 7- T + 1- T-1-...Song/T
Although the order is T track, the order is limited to Q, N-1°N Nm T+1. ... A similar effect can be obtained by using the order of the cho-jyu-cho tracks.

If N is an odd number, the first accessed N+1 alternative track (3) may be set as the -1 or N-1 track, and thereafter, the tracks may be alternately advanced in the inner and outer circumferential directions or in the outer and inner circumferential directions.

〔Effect of the invention〕

As described above, in this invention, since the substitute track is arranged in the radial center of the magnetic disk, the maximum moving distance of the magnetic head from the defective track to the substitute track is shortened.
The maximum reading time of recorded data is significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing allocated areas of tracks of a magnetic disk of a magnetic disk control device in an embodiment of the present invention;
FIG. 2 is a diagram showing allocated areas of tracks of a conventional magnetic disk, and FIG. 3 is a diagram showing addresses of the magnetic disk of FIG. 2. In the figure, (1) is a magnetic disk, (2) is a track used by a user, (2a) is a defective track, and (3) is a substitute track. In each figure, the same reference numerals indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 1 J: I＼Minna■Rack

Claims (1)

[Scope of Claims] A magnetic disk in which a plurality of tracks for recording information are formed concentrically, and a magnetic head that is controlled to drive in the radial direction of the magnetic disk to access each of the tracks, the accessed track 1. A magnetic disk control device which sequentially selects a pre-specified alternative track when the track is a defective track due to a defect in a disk medium, wherein the alternative track is arranged at the center in the radial direction of the magnetic disk.