JP2016170841A - Magnetic disk drive and magnetic disk control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk drive capable of detecting off track of a head at an appropriate timing and a magnetic disk control method.SOLUTION: A magnetic disk drive 1 includes magnetic disks 2, heads 3, and a controller 4. The magnetic recording layer of the magnetic disk 2 is divided into tracks 2a. Each track 2a is divided into plural as a sector 2b in a rotation direction. An additional region 2c corresponding to each sector 2b is provided in the magnetic disk 2. The controller 4 has a write controller 5. The write controller 5 performs control to write user data into each sector 2b. The write controller 5 further performs control to write additional information on the sector 2b into which user data is written into the additional region 2c corresponding to the sector 2b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic disk device and a magnetic disk control method, and more particularly to a magnetic disk device and a magnetic disk control method for recording information in a sector provided on a magnetic disk.

  The storage capacity of a magnetic disk drive (HDD) is increasing every year. In order to increase the recording capacity of the magnetic disk device, it is necessary to improve the recording density of the magnetic disk. Therefore, the values of linear recording density (BPI: bit per inch) and track density (TPI: track per inch) are increasing year by year.

  When increasing the number of sectors arranged on one track by increasing the linear recording density, the arrangement of sector servo information (servo information) used for head positioning control becomes a problem. If a large amount of sector servo information is arranged, the accuracy of the head positioning control is improved, but a large number of sectors cannot be arranged. Conversely, if a large number of sectors are arranged, the sector servo information is reduced, the head positioning accuracy is lowered, and head misalignment cannot be detected in a timely manner. Thus, there is a conflicting relationship between the number of sectors that can be arranged in one track and the number of sector servo information.

  In a magnetic disk device whose capacity is increasing, the number of sector servo information is reduced to the very minimum, and the number of sectors arranged between the sector servo information is increased. On the other hand, increasing the frequency of obtaining sector servo information is one method for performing head positioning control with high accuracy using only sector servo information. However, the maximum value of the sector servo information acquisition frequency has a limit, and cannot be larger than a certain value. Even if the frequency of obtaining the sector servo information is increased, the head positioning control deviation due to disturbance factors such as sudden vibration or impact cannot be detected immediately, and therefore the recovery process is delayed. As a result, the magnetic field in data writing may affect adjacent tracks. Therefore, it is desired to detect the off-track at an appropriate timing so that the head position can be returned to the target track when an off-track in which the head deviates from the target track occurs.

  In relation to the above technique, Patent Document 1 discloses a digital data reproduction method for improving the reliability of reproduction data in a technique for reproducing digital data from a disk-shaped recording medium. In Patent Document 1, user data is divided by a predetermined unit, and an ECC block is composed of 16 sectors to which an incremented sector number and an error detection code are added, and an error correction code of an inner code and an outer code. The data added with is reproduced from the disc-shaped recording medium and corrected. When correction becomes impossible, it is regarded as a track shift, and error correction by the inner code is performed again, but the flag information by the inner code of the sector determined as “error present” by the error detection code or the sector number continuity check, Rewrite from “no error” to “with error”, and then correct according to the outer code and flag information.

JP 2005-228417 A

  The technique according to Patent Document 1 only detects and corrects errors, but does not detect the head position. Therefore, the technique according to Patent Document 1 cannot detect head off-track at an appropriate timing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic disk apparatus and a magnetic disk control method capable of detecting head off-track at an appropriate timing. .

  A magnetic disk device according to the present invention includes a magnetic disk in which each track, which is a storage area in which a magnetic recording layer formed on a disk is concentrically divided into a plurality of tracks, is further divided into a plurality of sectors in the rotational direction; A head used for writing and reading information to and from the magnetic disk; and a control unit for performing control for writing and reading information using the head. An additional area corresponding to each sector is provided, and the control unit writes user data to each sector, and adds additional information related to the sector in which the user data is written and the position of the corresponding sector. Control is performed to write additional information including at least the indicated position information in the additional area corresponding to the sector. Having a write control means.

  In the magnetic disk control method according to the present invention, each track, which is a storage area obtained by concentrating the magnetic recording layer formed on the disk into a plurality of concentric circles, is further divided into a plurality of sectors in the rotational direction. User data is written in each of the sectors of the magnetic disk provided with an additional area corresponding to the information, and at least position information indicating the position of the corresponding sector is additional information relating to the sector in which the user data is written. The additional information included is written in the additional area corresponding to the sector, the additional information is read from the additional area, and the magnetic disk is read based on the position information included in the additional information read from the additional area. Check whether the head for writing and reading information is in an off-track state. To.

  According to the present invention, it is possible to provide a magnetic disk device and a magnetic disk control method capable of detecting head off-track at an appropriate timing.

It is a figure which shows the outline | summary of the magnetic disc apparatus concerning this Embodiment. 1 is a diagram showing a magnetic disk device according to a first exemplary embodiment; FIG. 3 is a diagram showing the magnetic disk shown in FIG. 2. FIG. 6 is a diagram for explaining the operation of the write control unit according to the first embodiment; FIG. 3 is a diagram illustrating a configuration of a read control unit according to the first embodiment. It is a figure which shows the state which the head moved to the position other than the objective. It is a figure which shows the state which the head moved to the position other than the objective. 4 is a flowchart showing an off-track detection method in the magnetic disk control method according to the first embodiment; FIG. 6 is a diagram illustrating an example for explaining additional information reading processing according to the first embodiment; FIG. 10 is a diagram illustrating an example for explaining a reading process of additional information when there is a reading request according to the first embodiment; FIG. 10 is a diagram illustrating an example for explaining additional information read processing when a write request is made according to the first embodiment; 4 is a flowchart showing a data error detection method in the magnetic disk control method according to the first exemplary embodiment; FIG. 6 is a diagram illustrating a specific example for explaining data error detection processing according to the first exemplary embodiment;

(Outline of this embodiment)
Prior to the description of the embodiment, an outline of the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an outline of a magnetic disk device 1 according to the present embodiment. The magnetic disk device 1 includes a magnetic disk 2, a head 3, and a control unit 4.

  The magnetic disk 2 has a disk, and a magnetic recording layer is formed on the disk. This magnetic recording layer is divided into tracks 2a which are a plurality of concentric storage areas. Further, each track 2a is divided into a plurality of sectors 2b in the rotation direction. Further, the magnetic disk 2 is provided with an additional area 2c corresponding to each sector 2b.

  The head 3 is used for writing and reading information on the magnetic disk 2. The control unit 4 performs control for writing and reading information using the head 3. Further, the control unit 4 has a write control unit 5 (write control means). The write control unit 5 performs control for writing user data to each sector 2b. The write control unit 5 further performs control for writing additional information related to the sector 2b in which user data is written in the additional area 2c corresponding to the sector 2b. Here, the additional information includes at least position information indicating the position of the corresponding sector 2b.

  The magnetic disk device 1 according to the present embodiment is configured to write additional information including position information of the sector 2b to the additional area 2c when writing user data to the sector 2b of the magnetic disk 2. By using this additional information, the off-track of the head 3 can be detected at an appropriate timing. Even in the magnetic disk control method corresponding to the magnetic disk device 1, it is possible to detect the off-track of the head 3 at an appropriate timing.

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a diagram illustrating the magnetic disk device 10 according to the first embodiment. The magnetic disk device 10 includes a head 12, a magnetic disk 20, and a control unit 100. The magnetic disk 20 corresponds to the magnetic disk 2 shown in FIG. The head 12 corresponds to the head 3 shown in FIG. The head 12 faces the magnetic disk 20 and is used to write and read information on the magnetic disk 20.

  FIG. 3 is a diagram showing the magnetic disk 20 shown in FIG. The magnetic disk 20 has the same configuration as the magnetic disk 2 shown in FIG. That is, the magnetic disk 20 has a disk, and a magnetic recording layer is formed on the disk. The magnetic recording layer is divided into tracks 30 which are a plurality of concentric storage areas. Furthermore, each track 30 is divided into a plurality of sectors 32 in the rotational direction. Further, the magnetic disk 20 is provided with an additional area 34 corresponding to each sector 32 for each sector 32. Further, the magnetic disk 20 is provided with a plurality of servo information 22 used for positioning control of the head 12 in a radial manner.

  In other words, on the medium surface of the magnetic disk 20 facing the head 12, a track 30 for recording data (the locus of the head on the medium by the rotation of the medium) is arranged. In addition, a sector 32 that divides the track 30 by the minimum unit of data recording is arranged. Further, an additional area 34 for recording additional information 40 is provided for each sector 32 serving as a minimum data recording unit. FIG. 3 shows an additional area 34-0 corresponding to the sector 32-0, an additional area 34-1 corresponding to the sector 32-1, and an additional area 34-N corresponding to the sector 32-N. Here, N is an integer indicating the number of sectors 32. Further, if K is an arbitrary integer equal to or smaller than N, “sector #K” corresponds to sector 32-K. Furthermore, “additional area #K” corresponds to the additional area 34-K. In the present embodiment, the additional area 34 is provided after the corresponding sector 32, but is not limited thereto.

  In the additional area 34-K, additional information 40 corresponding to the corresponding sector 32-K is recorded. As will be described later, the additional information 40 is recorded in the additional area 34 by the writing control unit of the control unit 100. The additional information 40 includes at least physical sector position information 42 and a write command number 44. The physical sector position information 42 is information indicating the physical position (physical sector position) of the sector 32 -K on the magnetic disk 20. The physical sector position information 42 may indicate, for example, a physical block number (PBN). For example, in the physical sector position information 42, the sector 32-K is the sector 32 of which position (on which position) on the track 30 of which position from the center of the disk (platter). May be indicated. The physical sector position information 42 may be information indicating a position including the physical position of the sector 32 and the physical position of the corresponding additional area 34. The write command number 44 is identification information (write request identification information) for identifying a request (write request) for writing certain user data. Details will be described later.

  In response to a write request from a higher-level device (not shown), the control unit 100 includes a user included in the write request in the area (a plurality of sectors 32) on the magnetic disk 20 specified by the write request. Controls to write data. In addition, the control unit 100 responds to a request (read request) for reading certain user data from the host device from the area (a plurality of sectors 32) on the magnetic disk 20 specified by the read request. Control to read data. Details will be described below.

  The control unit 100 includes a table storage unit 102, a head position control unit 104 (head position control unit), a write control unit 110 (write control unit), a read control unit 120 (read control unit), and an off-track. It has a detector 140 (off-track detector) and a data error detector 150 (data error detector). The table storage unit 102 stores a table that associates an area (designated area) designated in the write request and the read request with the physical sector position of the sector 32. Here, the designated area in the write request and the read request is indicated by, for example, a logical block number (LBN) which is a serial number. That is, in the write request and the read request, the target area is specified such as what number of logical block numbers. The table storage unit 102 may store, for example, a table in which logical block numbers (designated areas) are associated with physical block numbers (physical sector positions).

  The head position control unit 104 performs positioning control of the head 12. Further, the head position control unit 104 performs a recovery process for returning the head 12 to the target track 30 when the head 12 is out of the target track 30. The recovery process according to the present embodiment will be described later. The head position control unit 104 may perform positioning control (recovery processing) of the head 12 using the servo information 22. Specifically, the head position control unit 104 reads a head positioning control signal from the servo information 22 every time the head 12 passes the servo information 22 and confirms the position of the head 12. Then, the head position control unit 104 performs control so that the head 12 remains within the width of the track 30. Note that reading of the head positioning control signal from the servo information 22 may be performed using the read control unit 120.

  Further, the head position control unit 104 controls the head 12 to the position of the sector 32 (target sector) where user data is to be written in response to the write request, using a write request from the host device. . Specifically, the head position control unit 104 extracts a designated area included in the write request, and recognizes a physical sector position where user data is to be written, using a table stored in the table storage unit 102. Then, the head position control unit 104 controls to move the head 12 to the physical sector position.

  Similarly, the head position control unit 104 uses the read request from the host device to move the head 12 to the position of the sector 32 (target sector) from which user data is to be read in response to the read request. To control. Specifically, the head position control unit 104 controls the head 12 to move to the physical sector position corresponding to the designated area included in the read request.

  The head position control unit 104 also indicates a target sector signal indicating that at the timing when the head 12 faces (arrives) at the physical sector position (target sector) corresponding to the designated area included in the write request or read request. Is output to the write control unit 110 or the read control unit 120. In other words, the head position control unit 104 outputs a target sector signal to the write control unit 110 or the read control unit 120 at a timing when the head 12 passes through the target sector.

  In response to the write request, the write control unit 110 performs control for writing the user data to be written to the sector 32 at the physical sector position corresponding to the designated area designated by the write request. Specifically, the write control unit 110 controls the head 12 to write user data to the sector 32 when a target sector signal is received from the head position control unit 104. Furthermore, the write control unit 110 adds physical sector position information indicating the physical sector position of the sector 32 and a write command number for identifying a write request to the additional area 34 corresponding to each sector 32 into which user data has been written. The head 12 is controlled to write additional information including it. More specifically, the head 12 converts an electrical signal corresponding to user data to be written into a magnetic field under the control of the writing control unit 110. Thereby, the user data is recorded in the sector 32 by magnetizing the magnetic recording layer of the sector 32 to be written. The same applies to the writing of additional information. As described above, the write control unit 110 performs control for writing user data and additional information to the magnetic disk 20 every time a write request is received.

  FIG. 4 is a diagram for explaining the operation of the write control unit 110 according to the first embodiment. First, the write command number of the write request accepted by the control unit 100 is “write command # 0”, and in this write request, “sector # 1 to sector # 5 (actually these The logical block number corresponding to the sector 34) ”is designated. In this case, the write control unit 110 records user data corresponding to the write command # 0 in the sectors 32-1 to 32-5. Then, the write control unit 110 records additional information # 1 to # 5 in the additional areas 34-1 to 34-5, respectively.

  Here, the additional information # 1 includes physical sector position information indicating the physical sector position “physical sector position # 1” of the sector 32-1. Further, the additional information # 1 includes a write command number indicating “write command # 0”. Similarly, the additional information # 2 to # 5 includes physical sector position information indicating the physical sector positions “physical sector position # 2” to “physical sector position # 5” of the sectors 32-2 to 32-5, respectively. It is. Further, each of the additional information # 2 to # 5 includes a write command number indicating “write command # 0”.

  Next, the write command number of the write request accepted by the control unit 100 is “write command # 1”. In this write request, “sector # 6 to sector # 8” are designated as areas for writing user data. Suppose that In this case, the write control unit 110 records user data corresponding to the write command # 1 in the sectors 32-6 to 32-8. Then, the write control unit 110 records additional information # 6 to # 8 in the additional areas 34-6 to 34-8, respectively.

  Here, the additional information # 6 includes physical sector position information indicating the physical sector position “physical sector position # 6” of the sector 32-6. Further, the additional information # 6 includes a write command number indicating “write command # 1”. Similarly, the additional information # 7 to # 8 includes physical sector position information indicating the physical sector positions “physical sector position # 7” to “physical sector position # 8” of the sectors 32-7 to 32-8, respectively. It is. Further, each of the additional information # 7 to # 8 includes a write command number indicating “write command # 1”.

  In response to the read request, the read control unit 120 performs control for reading the user data to be read from the sector 32 at the physical sector position corresponding to the specified area specified by the read request. Specifically, the read control unit 120 performs control for reading user data from the plurality of sectors 32 when a target sector signal is received from the head position control unit 104. Further, the read control unit 120 performs control for reading the additional information written in the additional area 34. Here, the reading of the additional information is preferably performed when the control unit 100 receives a reading request and a writing request, but may be performed at an arbitrary timing. More specifically, the head 12 converts a magnetic field generated from the magnetic disk 20 (track 30) into an electrical signal. Then, the read control unit 120 demodulates (reproduces) the electrical signal into information at a timing at which the information is to be read.

  FIG. 5 is a diagram illustrating a configuration of the read control unit 120 according to the first embodiment. The read control unit 120 includes a user data read gate generation circuit 122, an additional information read gate generation circuit 124, an OR circuit 126, and a demodulation circuit 130. The demodulation circuit 130 receives from the head 12 an electrical signal converted from the magnetic field generated by the magnetic disk 20. The demodulating circuit 130 demodulates (reproduces) the electrical signal into information (user data and additional information) at the timing when the read gate signal is received.

  When the control unit 100 receives a read request from the host device, the user data read gate generation circuit 122 demodulates the electrical signal read from the read target sector 32 (target sector) by the head 12 into user data. A read gate signal is generated for the purpose. Specifically, the user data read gate generation circuit 122 is controlled by the head position control unit 104 when the head 12 faces the sector 32 (target sector) to be read from the target position control unit 104. Accept the signal. At this time, the user data read gate generation circuit 122 generates a read gate signal.

  The read gate generation circuit 124 for additional information is used from the additional region 34 by the head 12 not only when the control unit 100 receives a read request from the host device but also when a write request is received (and in other cases). A read gate signal for demodulating the read electrical signal into additional information is generated. Specifically, the additional information read gate generation circuit 124 generates a read gate signal every time the head 12 passes through the additional area 34.

  The OR circuit 126 outputs the read gate signal to the demodulation circuit 130 at the timing when the read gate signal is received from at least one of the user data read gate generation circuit 122 or the additional information read gate generation circuit 124. Thereby, the demodulation circuit 130 demodulates the electrical signal read from the target sector into user data. Then, the demodulation circuit 130 outputs the demodulated user data to the higher-level device. On the other hand, the demodulation circuit 130 demodulates the electrical signal read from the additional area 34 into additional information. Then, the demodulation circuit 130 outputs the demodulated additional information to the off-track detection unit 140 and the data error detection unit 150.

  The off-track detection unit 140 detects whether the head 12 is positioned on the target track 30 using the physical sector position information included in the read additional information. In other words, the off-track detection unit 140 detects whether the head 12 is in an off-track state. Then, when the head 12 is in an off-track state, the off-track detection unit 140 instructs the head position control unit 104 to adjust the head 12 to the target track 30 position. Details will be described later. The cause of the off-track of the head 12 is, for example, an influence as shown in FIGS. 6 and 7 described later, but is not limited thereto.

  The data error detection unit 150 detects whether there is an error in the user data read in response to the read request. Specifically, when user data is written, there is a case where data cannot be normally written to the target sector 32 (data error) due to the influence as shown in FIGS. 6 and 7 described later. . Further, there may be a case where it is considered that the user data has been normally terminated due to a failure of the control program (firmware) of the magnetic disk device 10 because it has not been detected that user data has been written. In this case also, a data error has occurred. When data cannot be normally written in this way, incorrect data (or empty data) is recorded in the sector 32. In this case, when user data is read, incorrect data (old data) is mixed in the read user data. When user data mixed with incorrect data is output to the host device, data corruption or file reading error occurs.

  In order to prevent this data corruption, the data error detection unit 150 detects whether or not this data error has occurred using the write command number included in the read additional information. Then, the data error detection unit 150 instructs the reading control unit 120 to stop the reading process when detecting that a data error has occurred. Details will be described later.

  6 and 7 are views showing a state in which the head 12 has moved to an undesired position. As shown in FIG. 6, the head 12 may be separated from the surface 20 a of the magnetic disk 20 in the vertical direction as indicated by an arrow A due to vibration of the magnetic disk device 10 or dust or the like that has entered the magnetic disk device 10. is there. Further, as shown in FIG. 7, the head 12 may be displaced in the horizontal direction from the width of the track 30 due to vibration of the magnetic disk device 10 or the like. In such a case, the head 12 is off-tracked.

  If the state shown in FIG. 6 or FIG. 7 occurs during the reading process, the head 12 is away from the target sector 32 (track 30), so that user data may not be read correctly. There is. Further, when the state shown in FIG. 6 or FIG. 7 is reached during the writing process, the strength necessary for writing data to the target sector 32 (track 30) on the disk of the magnetic disk 20 is obtained. In other cases, the target sector cannot be magnetized normally. This can cause data errors.

  Therefore, this embodiment is configured to detect the off-track state of the head 12 at an appropriate timing, as will be described below. The present embodiment is configured to detect whether or not a data error has occurred in the read user data, as will be described below.

  FIG. 8 is a flowchart of the off-track detection method in the magnetic disk control method according to the first embodiment. First, the magnetic disk device 10 writes user data in the sector 32, and writes additional information in the additional area 34 corresponding to the sector 32 (S102). Specifically, as described above, when the write request is accepted, the write control unit 110 controls to write the user data to the sector 32 to be written. At that time, the write control unit 110 controls to write the additional information as described above in the additional area 34 corresponding to the sector 32.

  Next, the magnetic disk device 10 reads additional information from the additional area 34 (S104). Specifically, the read control unit 120 reads (reproduces) the additional information using the read gate signal as described above. This additional information reading process can be performed at an arbitrary timing as shown in FIGS.

  Next, the magnetic disk device 10 detects whether or not the head 12 is in an off-track state using the physical sector position information included in the read additional information (S106). At this time, the magnetic disk device 10 confirms the position of the head 12 by reading the physical sector position information from the additional area 34 corresponding to the sector 32 that is the off-track detection target. If the head 12 is in an off-track state (YES in S106), the magnetic disk device 10 performs a recovery process for adjusting the head 12 to the position of the target track 30 (S108).

  Specifically, the off-track detection unit 140 compares the physical sector position information included in the read additional information with the position information indicating the position where the head 12 is to be controlled at that time. Here, “position information indicating the position where the head 12 is to be controlled” can be acquired from, for example, the head position control unit 104 that controls the position of the head 12. Then, the off-track detection unit 140 deviates from the position of the target track 30 when the physical sector position information included in the additional information is different from the position information indicating the position where the head 12 is to be controlled. (For example, the state of FIG. 7). Accordingly, at this time, the off-track detection unit 140 instructs the head position control unit 104 to return the head 12 to the position of the target track 30. As a result, the head position control unit 104 performs a recovery process. In the case where the off-track detection unit 140 cannot continuously read the additional information from the additional area 34, the head 12 is separated from the surface of the magnetic disk 20 in the vertical direction (for example, the state of FIG. 6). You may judge. Also at this time, the off-track detection unit 140 may instruct the head position control unit 104 to perform the recovery process.

Hereinafter, a specific example will be described.
FIG. 9 is a diagram illustrating an example for explaining the additional information reading process according to the first embodiment. As shown in FIG. 9, the sector 32 and the additional area 34 are provided between the servo information 22. As described above, every time the head 12 passes the servo information 22, the head position control unit 104 performs positioning control of the head 12. Further, in the present embodiment, even between the servo information 22, the position of the head 12 is deviated from the target track 30 by reading the additional information from each of the additional areas 34 arranged between the servo information 22. It is configured to detect whether or not.

  Specifically, as illustrated in FIG. 9, the additional information read gate generation circuit 124 of the read control unit 120 generates a read gate signal at each timing when the head 12 faces the additional regions 34-1 to 34-8. Generate. Thereby, the read control unit 120 reproduces the additional information # 1 to # 8. The off-track detection unit 140 detects whether or not the head 12 is in an off-track state for each of the additional information # 1 to # 8. That is, the off-track detection unit 140 detects whether or not the head 12 is in an off-track state at each timing when the head 12 faces the additional areas 34-1 to 34-8. In other words, in the present embodiment, whether the head 12 is in an off-track state not only when the head 12 passes the servo information 22 but also when the head 12 is positioned between the servo information 22. Detect whether or not. Therefore, in the present embodiment, it is possible to detect the off-track of the head 12 at an appropriate timing.

  FIG. 10 is a diagram illustrating an example for explaining the additional information reading process when there is a reading request according to the first embodiment. In the example of FIG. 10, it is assumed that there is a read request for reading user data recorded in sectors # 3 to # 5. At this time, before the sectors # 3 to # 5 to be read, the read control unit 120 reads the additional information # 1 to # 2 at the timing when the head 12 faces the additional areas 34-1 to 34-2. . Similarly to the above-described example, the off-track detection unit 140 performs off-track detection processing for each of the additional information # 1 and # 2.

  In the sectors # 3 to # 5 to be read, the read control unit 120 causes the read gate signal to be read by the user data read gate generation circuit 122 at a timing when the head 12 faces each of the sectors 32-3 to 32-5. Is generated. At this time, the read control unit 120 generates a read gate signal at a timing at which the head 12 faces each of the additional regions 34-3 to 34-5 by the additional information read gate generation circuit 124. The read control unit 120 reads (reproduces) the user data to be read from the sectors 32-3 to 32-5 and outputs the read user data to the host device. # 5 is read (reproduced). Similarly to the above-described example, the off-track detection unit 140 performs off-track detection processing for each of the additional information # 3 to # 5.

Further, even after sectors # 3 to # 5 to be read, the read control unit 120, at the timing when the head 12 faces the additional areas 34-6 to 34-8, similarly to the sectors # 1 to # 2. Read additional information # 6 to # 8. Then, the off-track detection unit 140 performs off-track detection processing for each of the additional information # 6 to # 8.
In this way, in the present embodiment, when there is a read request, the control unit 100 can detect the off-track of the head 12 using the additional information while reading the user data to be read. Become.

  FIG. 11 is a diagram illustrating an example for explaining the additional information reading process when there is a write request according to the first embodiment. In the example of FIG. 11, it is assumed that there is a write request (write command #Z) for writing user data in sectors # 4 to # 5. At this time, in the same manner as in the above-described example, the read control unit 120 adds the read before the write target sectors # 4 to # 5 at the timing when the head 12 faces the additional areas 34-1 to 34-3. Read information # 1 to # 3. Then, the off-track detection unit 140 performs off-track detection processing for each of the additional information # 1 to # 3.

  In the write target sectors # 4 to # 5, the write control unit 110 performs control for writing user data corresponding to the write command #Z to the sectors 32-4 to 32-6. Further, the writing control unit 110 performs control for writing the additional information # 4 to # 5 in the additional areas 34-4 to 34-6. Accordingly, since the additional information is rewritten, the additional information is not read out in the sectors # 4 to # 5 to be written. That is, the off-track state detection process is not performed in the write target sectors # 4 to # 5.

On the other hand, after the user data is written in the sectors # 4 to # 5 to be written, as in the sectors # 1 to # 3, at the timing when the head 12 faces the additional areas 34-6 to 34-8, The read control unit 120 reads the additional information # 6 to # 8. Then, the off-track detection unit 140 performs off-track detection processing for each of the additional information # 6 to # 8.
Thus, in this embodiment, when there is a write request, the control unit 100 detects the off-track of the head 12 using the additional information for the sectors 32 before and after the sector 32 to be written. It becomes possible to do.

  FIG. 12 is a flowchart of the data error detection method in the magnetic disk control method according to the first embodiment. First, similarly to the process of S102, the magnetic disk device 10 writes user data in the sector 32, and writes additional information in the additional area 34 corresponding to the sector 32 (S202). Note that when writing user data, there is a possibility that data has not been written normally due to the influence shown in FIGS.

  If there is a read request (YES in S204), the magnetic disk device 10 reads the user data to be read from the sector 32 to be read, and reads additional information from the additional area 34 corresponding to the sector 32 ( S206). Specifically, as described above, the read control unit 120 reads (reproduces) user data and additional information using the read gate signal.

  Next, the magnetic disk device 10 detects whether or not a data error has occurred in the user data by using the write command number included in the read additional information (S208). Specifically, the data error detection unit 150 writes each additional information read from a plurality of continuous additional areas 34 corresponding to each of a plurality of continuous sectors 32 in which the read user data is recorded. Check the command number. Then, the data error detection unit 150 determines whether or not the plurality of write command numbers are all the same. When the plurality of write command numbers are all the same, the data error detection unit 150 determines that no data error has occurred. On the other hand, if at least one of the plurality of write command numbers is different from the other write command numbers, the data error detection unit 150 determines that a data error has occurred for the user data.

  If a data error has occurred (YES in S208), the magnetic disk device 10 stops the read process for the read request (S210). Specifically, the data error detection unit 150 instructs the reading control unit 120 to stop the reading process when detecting that a data error has occurred. Thereby, the read control unit 120 stops the read process. Accordingly, since incorrect data is not output to the host device, it is possible to prevent data corruption. On the other hand, if no data error has occurred (NO in S208), the data error detection unit 150 does not instruct to stop the reading process, and the magnetic disk device 10 normally ends the reading process (S212).

Hereinafter, a specific example will be described.
FIG. 13 is a diagram illustrating a specific example for explaining the data error detection processing according to the first embodiment. First, as shown in FIG. 4, user data corresponding to the write command # 0 is recorded in the sectors 32-1 to 32-5 by the write command # 0. Further, additional information including a write command number indicating write command # 0 is recorded in additional areas 34-1 to 34-5 corresponding to sectors 32-1 to 32-5, respectively. Similarly, user data corresponding to the write command # 1 is recorded in the sectors 32-6 to 32-8 by the write command # 1. Further, additional information including a write command number indicating the write command # 1 is recorded in the additional areas 34-6 to 34-8 corresponding to the sectors 32-6 to 32-8, respectively.

  Assume that there is a write request (write command #X) for writing in sectors # 2 to # 5 in this state. At this time, the head 12 is controlled to the positions of the sectors 32-2 to 32-5 by the head position control unit 104, and the write control unit 110 controls to write the user data to the sectors 32-2 to 32-5. .

  At this time, if normal, user data corresponding to the write command #X is recorded in the sectors 32-2 to 32-5. That is, the user data corresponding to the write command # 0 is rewritten to the user data corresponding to the write command #X. In this case, additional information including a write command number indicating the write command #X is recorded in the additional areas 34-2 to 34-5. Therefore, the data error detection unit 150 determines that all the write command numbers read from the additional areas 34-2 to 34-5 are the same (write command #X). Therefore, the data error detection unit 150 determines that no data error has occurred.

  Here, it is assumed that when the head 12 is opposed to the position of the sector 32-3, a write error that is not normally written has occurred due to the influence shown in FIGS. In this case, user data corresponding to the write command #X is not recorded in the sector 32-3. That is, old user data corresponding to the write command # 0 is still recorded in the sector 32-3. At this time, the user data read from the sector 32-3 is not correct data, and therefore a data error has occurred in the sector 32-3. In this state, it is assumed that there is a user data read request corresponding to the write command #X. In this case, when user data is read from the sectors 32-2 to 32-5 to read the user data corresponding to the write command #X, the user data read from the sector 32-3 is not correct data. Therefore, if the data read from the sector 32-3 is output to the host device, data corruption occurs.

  On the other hand, in this embodiment, as shown in FIG. 13, the write command number indicating the write command # 0 is recorded in the additional area 34-3. Therefore, the data error detection unit 150 includes the write command number read from the additional area 34-3 (write command # 0) among the write command numbers read from the additional areas 34-2 to 34-5. It is determined that the write command number (write command #X) read from the other additional areas 34-2, 34-4, and 34-5 is different.

  In other words, the write control unit 110 receives a plurality of user data (first user data) corresponding to the write command #X in response to the write command #X (first write request). Control is performed so as to write to sectors 32-2 to 32-5. At this time, the write control unit 110 writes the write command number (the first command number) indicating the write command #X to a plurality of consecutive additional areas 34-2 to 34-5 corresponding to the plurality of sectors 32-2 to 32-5. 1 write request identification information). When there is a read request for the first user data, the read control unit 120 controls to read the first user data from a plurality of consecutive sectors 32-2 to 32-5. At this time, the read control unit 120 controls to read additional information from the additional areas 34-2 to 34-5 corresponding to the plurality of sectors 32-2 to 32-5, respectively. The data error detection unit 150 then selects at least one of the write command numbers read from the additional areas 34-2 to 34-5 (in this example, the write command number read from the additional area 34-3). Does not indicate the write command number indicating the write command #X, it is detected that a data error has occurred for the first user data.

  As a result, the data error detection unit 150 can determine that a data error has occurred in the sector 32-3. Thereby, in the first embodiment, it is possible to prevent data corruption.

  Generally, the positioning control of the head 12 is performed by an embedded servo system that acquires servo information 22 radially recorded on a medium (magnetic disk 20) at a specific period. In this method, positioning control is performed for each specific period in which the head 12 passes the servo information 22, and the position information of the head 12 cannot be acquired between the servo information 22. Therefore, the position of the head 12 cannot be confirmed between the servo information 22, and positioning control cannot be performed.

  On the other hand, in the present embodiment, additional information is recorded in each additional area 34 corresponding to each sector 32. Therefore, it is possible to detect the off-track state of the head 12 by reading this additional information and using the physical sector position information included in the additional information even between the servo information 22. In other words, after the head 12 passes through the servo information 22, the additional information is read from the additional area 34 provided corresponding to each sector 32 without waiting for the head 12 to reach the next servo information 22. The off-track state of the head 12 can be detected. As a result, the period for performing the positioning control (adjusting the head 12 to the target track 30) is shorter than when the positioning control of the head 12 is performed using only the servo information 22. Therefore, the position of the head 12 can be adjusted at an appropriate timing.

  In other words, in the present embodiment, the additional information is read out and used to detect the off-track state, so that the influence of vibration or impact or the impact of dust inside the magnetic disk device 10 on the head 12 (FIG. 6). 7) and the like can be detected at a specific period corresponding to the interval between the additional regions 34. Accordingly, it is possible to detect that the head 12 is in an off-track state at an early stage before the head 12 passes the servo information 22.

  Note that it is conceivable to arrange a lot of servo information 22 if the cycle for performing the positioning control is simply shortened (the frequency of positioning control is increased). However, since the servo information 22 is read on the disk of the magnetic disk 20 at the same period on the inner circumference side and the outer circumference side, the servo information 22 is recorded radially on the disk and becomes wider especially on the outer circumference side of the disk. Thus, if a large amount of servo information 22 is arranged, a large number of sectors 32 cannot be arranged (especially on the outer periphery side where a large amount of data can be recorded).

  On the other hand, the data amount of the additional information in the present embodiment can be made very small as compared with the data amount of user data recorded in the corresponding sector 32. Therefore, even if the additional area 34 is provided for each sector 32, the additional area 34 can be made very small compared to the sector 32. Therefore, it is possible to provide the additional area 34 without reducing the number of sectors 32 for recording user data. Therefore, when the off-track state of the head 12 is to be detected at the same period, the number of sectors 32 can be increased by providing the additional area 34 as compared with the case where a lot of servo information 22 is arranged. .

  Further, when executing a write request (write command), the magnetic disk device writes user data in batches to designated consecutive sectors. At this time, generally, the execution order (write request identification information) of the write command is not recorded. Therefore, the continuity of sectors in which user data is written by one write command cannot be confirmed. In general, except for the command for verifying the written user data, the magnetic disk device determines that the data has been normally written unless an abnormality is detected during data writing, and the write command is Finish normally. However, even when the write command is completed normally, during the execution of the write command, the influence of vibration or impact or the influence of the dust that has entered the inside of the magnetic disk device and the collision with the head 12 (FIG. 6 and FIG. 6). FIG. 7) or the like or a malfunction of the firmware may not detect that data could not be written normally. In this case, old data remains in the sector 32 that has not been normally written. At this time, if the old data can be read normally by the read request, the old data is output to the host device. As a result, data corruption or file read error occurs.

  On the other hand, the magnetic disk device 10 according to the present embodiment is configured to record a write command number in the additional area 34 when writing user data. That is, the magnetic disk device 10 is configured to record the execution order of write commands in the additional area 34 when writing user data. Therefore, the execution order of the write command of the user data recorded in the sector 32 to be read can be confirmed using the write command number when reading the user data. Thereby, a data error of user data can be detected. Therefore, it is possible to prevent old data from being output to the host device.

(Modification)
Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the embodiment described above, the additional information includes the physical sector position information and the write command number, but the additional information includes only one of the physical sector position information and the write command number. It may be. The additional information can also include information other than these. For example, the additional information can include other monitoring items or information to be confirmed.

  In the above-described embodiment, the additional area 34 is provided after the corresponding sector 32. However, the additional area 34 may be provided before the corresponding sector 32. In this case, the sector pulse waveform output to indicate the head position of each sector may be used instead of the read gate signal by the additional information read gate generation circuit 124.

  In the above-described embodiments, the present invention has been described as a hardware configuration, but the present invention is not limited to this. The present invention can also be realized by causing a CPU (Central Processing Unit) to execute a computer program for the processing of each circuit constituting the control unit 100 (the processing shown in FIGS. 8 and 12).

  In the above example, the program can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W, semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)) are included. The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

DESCRIPTION OF SYMBOLS 1 Magnetic disk apparatus 2 Magnetic disk 2a Track 2b Sector 2c Additional area 3 Head 4 Control part 5 Write control part 10 Magnetic disk apparatus 12 Head 20 Magnetic disk 22 Servo information 30 Track 32 Sector 34 Additional area 40 Additional information 42 Physical sector position Information 100 Control unit 102 Table storage unit 104 Head position control unit 110 Write control unit 120 Read control unit 140 Off-track detection unit 150 Data error detection unit

Claims (9)

A magnetic disk in which each track, which is a storage area in which a magnetic recording layer formed on a disk is concentrically divided into a plurality of sections, is further divided into a plurality of sectors in the rotation direction;
A head used for writing and reading information to and from the magnetic disk;
A control unit that performs control for writing and reading information using the head, and
The magnetic disk is provided with an additional area corresponding to each sector,
The controller is
User data is written in each sector, and additional information relating to the sector in which the user data is written and including at least position information indicating the position of the corresponding sector is added to the additional area corresponding to the sector. A magnetic disk device comprising write control means for performing control for writing. The controller is
Read control means for performing control for reading the additional information from at least the additional area;
The magnetic disk according to claim 1, further comprising: an off-track detection unit that detects whether the head is in an off-track state based on the position information included in the additional information read from the additional area. apparatus. The controller is
The magnetic disk apparatus according to claim 2, further comprising a head position control unit that adjusts the head to a target track position when the head is in an off-track state. The off-track detection unit is configured such that a position indicated by the position information included in the read additional information is different from a position where the head is to be controlled when the additional information is read. The magnetic disk device according to claim 2, wherein off-track occurrence is detected. The write control means writes the user data to each sector in response to a write request for writing the user data, and adds additional information including write request identification information for identifying the write request to the sector. The magnetic disk device according to claim 1, wherein control for writing in the corresponding additional area is performed. The controller is
Read control means for reading the user data from each of the sectors and performing control for reading the additional information from the additional area corresponding to the sector;
The data error detecting means for detecting an error of the read user data based on the write request identification information included in the additional information read when the user data is read. 5. The magnetic disk device according to 5. The write control means writes first user data to a plurality of consecutive sectors in response to a first write request, and writes the first user data to the plurality of consecutive additional areas corresponding to the plurality of sectors, respectively. Control for writing the first write request identification information indicating the write request of
The reading control means reads the first user data from the plurality of consecutive sectors, and performs control for reading the additional information from the plurality of consecutive additional areas corresponding to the sectors,
The data error detection means may be configured such that at least one of the plurality of write request identification information included in each of the plurality of additional information read from the plurality of consecutive additional areas is the first write The magnetic disk device according to claim 6, wherein when the request identification information is not indicated, it is detected that an error has occurred in the first user data. A magnetic disk in which each track, which is a storage area obtained by concentrically dividing a magnetic recording layer formed on a disk into a plurality of tracks, is further divided into a plurality of sectors in the rotation direction, and an additional area corresponding to each sector is provided. In addition to writing user data in each of the sectors, additional information relating to the sector in which the user data has been written and additional information including at least position information indicating the position of the corresponding sector is included in the additional area corresponding to the sector. Write on the
Read the additional information from the additional area,
Magnetic disk control for detecting whether or not a head for writing and reading information to and from the magnetic disk is in an off-track state based on position information included in the additional information read from the additional area Method. A write request that writes the user data in response to a write request for writing the user data to each of the sectors, and is additional information regarding the sector in which the user data is written and identifies the write request Write additional information including identification information in the additional area corresponding to the sector,
When the user data is read from each of the sectors, the additional information is read from the additional area corresponding to the sector,
The magnetic disk control method according to claim 8, wherein an error in the read user data is detected based on the write request identification information included in the additional information read when the user data is read. .

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