JPH05128735A - Defective block alternation control system - Google Patents

Abstract

PURPOSE:To shorten the access time in the defective block replacement control system for an external storage device having a magnetic disk device. CONSTITUTION:This system is provided with a defective block detecting means 10A, which detects whether a defective block exists or not by verify operation after formatting of a recording medium, and a reformatting means 10B which assigns an adjacent block physically connected to a defective block as an alternate block at the time of detecting the defective block and reformats the recording medium. Thus, the overhead for access to the alternate block is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defective block alternation control system for an external storage device having a magnetic disk device. When a defective block in which data cannot be read or written normally due to a defect created during manufacturing of the recording medium or deterioration of magnetic recording characteristics is detected, the format of the recording medium (initialization) When performing, the replacement block (block to be used as a substitute for the defective block) is allocated.

In this case, it is necessary to minimize the overhead when accessing the alternate block and shorten the access time.

[0003]

2. Description of the Related Art In an external storage device having a magnetic disk device, the storage capacity per block is fixed, and a general area in which data can be read and written from a host device Logically consecutive addresses (LBA:
If a logical block address is attached, a spare block group is prepared in advance in an area different from the general area, and when a defective block is found in the general block, the block to be used as a substitute for the defective block ( Alternate blocks) are assigned from this spare block group.

When the host device issues a data read or write command to the area including the defective block, the read or write processing is not performed on the defective block, but a replacement assigned as a substitute for the defective block. By controlling the blocks to perform read or write processing, even if some blocks in the general area could not normally read or write data for some reason, all the logically continuous data from the host device A method is provided for making blocks available.

However, in general, a spare block group used for alternation allocation processing is an area different from the general area (alternate processing block prepared in advance for each track or cylinder = spare block, or alternate processing block). Cylinder where the group exists = alternate cylinder, etc.). Therefore, when the host device issues an instruction to read or write data to a plurality of blocks including a defective block that has undergone the alternate allocation process, the defective block is replaced with a spare block or a replacement block in the alternate cylinder. Since the allocation process was performed, the internal operation of the magnetic disk device is that after the continuous processing is performed from the first block to be processed to the block immediately before the defective block, the position of the alternate block that has been alternately allocated to this defective block. The head is positioned at (seek) to process this alternate block, and then the head is positioned at the position of the block immediately after the bad block and the blocks immediately after the bad block to the last block to be processed are processed consecutively. To do.

In this case, the time required to position the head on the track on which the alternate block exists varies depending on the seek distance (the number of cylinders), and the head is actually positioned on the track on which the alternate block exists. The time until the alternate block is processed (disk rotation waiting time) changes depending on the position of the alternate block on this track and the rotation speed of the disk, but generally it is several tens of millimeters compared to the case where no bad block exists. It requires a long processing time of about 2 seconds.

When formatting a recording medium, a verify operation (Certification) is specified, and when it is detected that a defective data block exists in the verify operation, the alternation process is conventionally performed as described above. In addition, extra processing time is always required for blocks that have undergone alternation unless they are reformatted.

For example, as shown in FIG. 5, when it is detected that the block 6 is a defective block on the track, the spare block 6 is assigned to the block 6 as a replacement block, and therefore the block 0 is assigned. From block to block 5, the seek to the position of the spare block 6 is performed, the spare block 6 is processed, the process returns to block 7, and the last block 12 is continuously processed. For this reason, there is a problem that the overhead for accessing the alternate block becomes large and the access time is long.

The present invention has been made in view of such conventional problems, and an object thereof is to shorten the access time by minimizing the overhead when accessing the alternate block.

[0010]

1A and 1B are explanatory views of the principle of the present invention. In FIG. 1A, reference numeral 2 denotes an external storage device having a magnetic disk device 8 and a microprocessor 10 for controlling the magnetic disk device 8.
Is a defective block detecting means for detecting the presence or absence of a defective data block by a verify operation after formatting the recording medium, and when a defective block is detected, a physically contiguous adjacent block is assigned as a substitute block for the defective block and reformatting is performed again It is a reformatting means.

[0011]

As shown in FIG. 1B, it is assumed that when the microprocessor formats according to an instruction from the host device, the track is formatted as shown in FIG. The logical address in the track is added to each block. Next, (b) shows that the verify operation is performed and it is detected that the block 6 has a defect. Next, (c) shows that physically adjacent contiguous blocks are assigned as a substitute block for block 6 and reformatting is performed. In this way, by using the position information of the defective data block detected by the verify operation, the defective block is physically located closest to the defective block within a track unit, a cylinder unit, or a plurality of cylinders, and the defective block is skipped. Reformatting to allocate continuously accessible blocks.

In general, spare sectors for alternation processing are prepared in advance in track units, cylinder units, or a plurality of cylinders. In this case, the blocks located after the defective block are replaced by the alternation process according to the present invention. The spare sector is used because it is shifted and formatted. As described above, when the verify operation after formatting the recording medium detects that there is a defective data block, and when a replacement process is performed on the block, when a read or write operation including the block is performed, Since physically adjacent contiguous blocks are assigned as replacement blocks for the defective block, in order to access the replacement block, it is only necessary to wait for the read or write operation until the defective block passes, so Compared with the case of seeking to the track in which the alternated block is located, the overhead of accessing the alternated block is reduced and the access can be performed at high speed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 4 are views showing an embodiment of the present invention.
In FIG. 2, 1 is a host device (host device) including a central processing unit, 2 is an external storage device, and 3 is a host interface connection line connecting the host device 1 and the external storage device 2.

Reference numeral 4 is a data buffer for temporarily storing data, 5 is a data buffer control unit for controlling the data buffer 4, 6 is an upper interface control unit, 7 is a lower interface control unit, and 8 is a lower interface control unit 7.
To the magnetic disk device 10 connected to the lower interface connection line 9 for controlling the magnetic disk device 8 or for controlling the input / output of the upper device 1 and the magnetic disk device 8; and 11 for the microprocessor 10.
The ROM and the program 12 stored therein are RAMs used when the microprocessor 10 operates.

The host device 1 has a host interface connection line 3
I / O commands are issued to the external storage device 2 through the I / O device to execute I / O operations. The data from the host device 1 is temporarily stored in the data buffer 4 and then accumulated in the magnetic disk device 8. The data stored in the magnetic disk device 8 is temporarily stored in the data buffer 4 and then sent to the host device 1.

Here, when the host device 1 instructs the external storage device 2 to format the recording medium, the microprocessor 10 controls the magnetic disk device 8 while controlling the lower interface controller 7 and the like. Format it. In addition, when performing a verify operation (Certification) after formatting, a verify operation is performed for all data blocks to be verified such as a general space (area accessible by the higher-level device 1) (data can be read normally). Confirm).

In this case, the microprocessor 10
The defective block detecting means 10A for detecting the presence or absence of a defective data block by the verify operation and the reformatting means 10B for allocating a physically continuous adjacent block as a substitute block and reformatting when a defective block is detected. It has the function of. Next, the operation will be described.

3 and 4 show the format within a cylinder. For convenience, it is assumed that there are four tracks d to g in one cylinder, ten blocks in one track, and three spare sectors in one cylinder. When the format is performed according to the instruction from the host device 1, the format is performed as shown in FIG.
Next, a verify operation is performed to perform blocks 11 and 34.
Suppose that a defect was detected in the. Next, as shown in FIG. 4, physically adjacent contiguous blocks are assigned as a substitute block for the blocks 11 and 34 and reformatting is performed. Block 11 according to an instruction from the host device 1
When there is a request for access including or, the defective blocks 11 and 34 are skipped and control is performed.

Therefore, in order to access the alternative block (blocks 11 and 33 in FIG. 4), it is only necessary to wait for the read or write operation until the defective block passes. As compared with the case of seeking to the track where is located, the overhead for accessing the alternated block is reduced and the access time can be shortened.

In this embodiment, when a defective block is detected at the time of formatting and replacement processing is performed on the defective block, only all the blocks in the cylinder in which the defective block exists are reformatted. When preparing a spare block for alternation processing in track units, reformatting may be performed in track units, or all blocks in the general space may be reformatted. Further, even when the higher-level device 1 instructs to perform the alternation process on a specific block, the same effect can be obtained by performing the alternation process as in this embodiment.

[0021]

As described above, according to the present invention,
Even when performing a read or write operation that includes a block that has been detected as a defective block at the time of formatting and has undergone alternation processing, access can be performed in approximately the same processing time as when there is no defective block, and access time can be shortened. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 shows a formatted track

FIG. 4 is a diagram showing a reformatted track.

FIG. 5 is an explanatory diagram of problems

[Explanation of symbols]

 1: Upper device 2: External storage device 3: Upper interface connection line 4: Data buffer 5: Data buffer control unit 6: Upper interface control unit 7: Lower interface control unit 8: Magnetic disk device 9: Lower interface connection line 10: Microprocessor 10A: defective block detection means 10B: reformatting means 11: ROM 12: RAM

Claims (1)

[Claims] 1. An external storage device (2) having a magnetic disk device (8) and a microprocessor (10) for controlling the magnetic disk device (8), wherein a defective data block is recorded by a verify operation after the recording medium is formatted. A defective block detecting means (10A) for detecting the presence / absence and a reformatting means (10B) for allocating a physically continuous adjacent block as a substitute block and reformatting when a defective block is detected are provided. Characteristic bad block replacement control method.