JP2010238315A - Data storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure data of adjacent tracks with respect to continuous writing of a certain track, in a data storage device that writes writing data on a recording medium by a head. <P>SOLUTION: The device is provided with: an erasing weight table (52) obtained by measuring a degree (weight) of side erasing within a measurement track range and registering it in a side erasing test process; a side erasing management table (56) that accumulates and stores weights of respective tracks during writing on a certain track; and a control circuit (11) that forcibly rewrites the track when the number of accumulated erasing points exceeds a prescribed number of points. This prevents data loss owing to side erasing including distant erasing, and also prevents the track from being unnecessarily rewritten. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a data storage device that reads / writes data to / from a storage medium using a head.

  Due to the recent demand for data digitization processing, it is required to increase the capacity of medium storage devices such as magnetic disk devices and optical disk devices that store data. For this reason, the disk medium has a higher track density and recording density.

  In such a data storage device, when data is continuously written to a certain track, the data of the peripheral tracks of the track is erased due to the influence of the leakage magnetic flux of the head. This phenomenon is called a side erase phenomenon. In particular, side erasure is likely to occur in perpendicular recording. Further, side erasure is likely to occur even in a magnetic storage medium having a high track pitch (for example, 200 kTPI = 200000 tracks / inch).

  In order to guarantee this side erase, a forced retry method is to detect that the same track has been written several times (for example, thousands or tens of thousands of times) and forcibly rewrite the data of the surrounding tracks. Has been proposed (see, for example, Patent Documents 1 and 2).

JP 2006-294231 A JP 2004-273060 A

  With recent increases in recording density and downsizing of the apparatus, the write current of the head has been increased in order to provide sufficient recording holding power. For this reason, it is in an environment where side erasure is likely to occur. The conventional side erase relief method is to forcibly write not only one track on both sides of one specific track that has been continuously written, but also the peripheral track (± 2 tracks).

  However, according to the investigation by the present inventors, the occurrence of erasure was confirmed not only in the peripheral track due to the write noise but also in a far track separated by 7 to 9 tracks depending on the head. In the above-described prior art, since the range of forced rewrite is the peripheral track, such a far erasure cannot be guaranteed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a data storage device that guarantees erasure of a distant track, prevents unnecessary forced rewrite, and prevents performance degradation.

  In order to achieve this object, the data storage device has a head for reading and writing data on a storage medium, an actuator for moving the head to an arbitrary track of the storage medium, and initially a track to be measured. The difference between the measured error rate of each track in a predetermined range and the measured error rate of each track in the predetermined range centered on the measurement target track after writing the measurement target track by the head a predetermined number of times. An erase weight table for storing the determined erase weight for each track, a side erase management table for storing an erase point for each track, and when the desired track is written, the erase weight table is referred to and the side erase is referred to. Accumulate erase points for the corresponding track in the management table, From the side erase management table, it is determined that there is a track with the number of erase points equal to or greater than the specified number of points, and the head performs a forced retry to read and rewrite the data of the track determined to exist. And a control circuit to be executed.

  In the side erase test process, the degree (weight) of the side erasure of each track is measured and registered within the measurement track range, and the erasure weight is accumulated when writing a track, and the accumulated erase point is the specified point. If the number is exceeded, the track is forcibly rewritten, so that it is possible to prevent data loss due to side erase including remote erase and to prevent unnecessary track rewrite.

It is a block diagram of one embodiment of a data storage device of the present invention. It is explanatory drawing of the side erase made into the object of this invention. It is explanatory drawing of the side erase measurement of one embodiment of this invention. It is explanatory drawing of the erase weight table of one embodiment of this invention. It is explanatory drawing of one Embodiment of the side erase management table of FIG. It is explanatory drawing of the erase weight table at the time of high temperature of other embodiment of this invention. It is explanatory drawing of the erase weight table at the time of normal temperature of other embodiment of this invention. It is explanatory drawing of the erase weight table at the time of low temperature of other embodiment of this invention. It is the side erase measurement processing flowchart (the 1) of one embodiment of this invention. It is the side erase measurement processing flowchart (the 2) of one embodiment of this invention. It is explanatory drawing of the side erase measurement location of one embodiment of this invention. It is a write processing flow figure of one embodiment of the invention.

  Hereinafter, embodiments of the present invention will be described in the order of a data storage device, side erase measurement processing, write processing, and other embodiments.

(Data storage device)
1 is a configuration diagram of an embodiment of a data storage device according to the present invention, FIG. 2 is an explanatory diagram of side erasure of FIG. 1, FIG. 3 is an explanatory diagram of side erase measurement processing, and FIG. 3 is an explanatory diagram of the erase point table of FIG. 3, and FIG. 5 is an explanatory diagram of the side erase management table of FIG. FIG. 1 shows a magnetic disk device (HDD) that reads / writes data on a magnetic disk as an example of a data storage device.

  As shown in FIG. 1, the magnetic disk device 10 is connected to a host 50 such as a personal computer via an interface such as a SATA (Serial AT Attachment) standard. The magnetic disk device 10 includes a disk enclosure 30 and a control board 40.

  The disk enclosure 30 includes a magnetic disk 19, a spindle motor 20 that rotates the magnetic disk 19, a magnetic head 25 that reads / writes data from / to the magnetic disk 19, and the magnetic head 25 in the radial direction of the magnetic disk 19 (track crossing). An actuator (VCM) 22 that moves in a direction) and a head IC 18.

  The control board 40 performs host interface control circuit 12 for controlling the interface with the host, buffer memory control circuit 15 for controlling the buffer memory (data buffer) 14, read / write control, and conversion of the recording data format. Drives a hard disk controller (HDC) 16 that performs reverse format conversion of read data, a read channel circuit 24, an MPU 11, a volatile memory (RAM) 13, a nonvolatile memory 17, a spindle motor 20, and a VCM 22. The motor drive control part 21 to control and the bus | bath 19 which connects these are provided.

  The host interface control circuit 12, the buffer memory control circuit 15, the HDC (Hard Disk Controller) 16, and the read channel circuit 24 are connected by a data bus. The read channel circuit 24 is connected to the head IC 18.

  The read channel circuit 24 demodulates read data and generates a read gate, a write gate, a read clock, and a write clock. The data buffer 14 serves as a cache memory, stores write data from the host, and stores read data from the magnetic disk 19. In write back, the write data in the data buffer 14 is written to the magnetic disk, and in read, the read data in the data buffer 14 is transferred to the host.

  The head IC 18 sends a recording current to the magnetic head 25 according to the write data at the time of writing, and amplifies the read signal from the magnetic head 25 at the time of reading and outputs it to the read channel circuit 24. An MPU (Micro Processor Unit) 11 performs position detection and position control of the magnetic head 25, command analysis from the host, access processing, retry control, and side erase processing.

  The volatile memory (RAM) 13 stores data necessary for the processing of the MPU 11. Here, an erase weight table 52 described in FIG. 4 and a side erase management table 56 described in FIG. 5 are also stored. A non-volatile memory (ROM) 17 stores programs and parameters necessary for processing of the MPU 11.

  The MPU 11 receives the servo signal of the magnetic disk 19 read by the magnetic head 25 from the head IC 18, detects the position of the head, seeks and on-track controls the VCM 22 via the motor drive control unit 21, and from the detected position Detect off-track.

  FIG. 2 is an explanatory diagram of side erasure. In a high temperature environment (60 ° C.), when data is continuously written to a track (cylinder) number “0” by a magnetic head, an error rate of data of adjacent ± 20 tracks is shown. The measurement results are shown. In FIG. 2, the horizontal axis is the track position, and the vertical axis is the error rate. The square mark in the figure indicates the error rate of each track when the number of writes of the track with the track number “0” is “0”, and the cross mark in the figure indicates the track number “0”. The error rate of each track when the number of writes is “100,000” is shown.

  As shown in FIG. 2, the error rate becomes high at the track position (± 2 to 3 track range) around the cylinder position “0” when writing 100,000 times (indicated by a cross). In addition, the error rate increases rapidly in the vicinity of a track position (cylinder position “−8”) that is 7 to 9 tracks away from the cylinder position “0”.

  This means that if a track is continuously written about 10,000 times, the data at the track position that is 7 to 10 tracks away from the track has a considerable effect and may be erased. Is high. That is, not only the peripheral tracks are erased but also the distant tracks are erased. This phenomenon also depends on the characteristics of the magnetic head, the recording current, and the temperature.

  In order to relieve such a side erase including a remote erase, for example, when writing is performed more than a specified number of times in a cell set (13 tracks), all the tracks in the cell set and the cell set A method of forcibly rewriting a total of 21 tracks corresponding to 4 tracks at both ends of the track is conceivable.

  However, as is clear from FIG. 2, even the tracks in this forced rewrite range are affected to a different extent, and almost all tracks that have not been erased may be subject to rewrite, possibly reducing performance. There is.

  For this reason, in the present embodiment, an error rate in a predetermined track range is measured in the side erase test, and the degree of influence on each track is determined from the measured error rate, and the weight of erase per write is calculated. As a point, decide. For each write, the erase point of each track is accumulated using the weight, and the track at the track position where the accumulated erase point has reached the specified value is rewritten.

  3 and 4 are explanatory diagrams of the side erase measurement process. As shown in FIG. 3, the error rate of the data of each track is measured in an initial state in which data is not written to the 0th track, for example, within a range of ± 10 tracks from the 0th track. In FIG. 3, the measurement results are indicated by diamond marks. Next, after writing data to the 0th track continuously, for example, 100,000 times, read data in a predetermined range (eg, ± 10 tracks) of track positions around the 0th track. Then, the error rate is measured. In FIG. 3, this result is indicated by a square mark.

  Then, for each track, the difference between the error rate measured in the initial state and the error rate measured after writing 100,000 times is calculated. This difference is the degree of erasure. The erase weight of each track is determined in proportion to this difference.

  FIG. 4 is an explanatory diagram of the erase weight table 52 of FIG. In this case, the erased weight of ± 5 tracks on both sides is shown with “0” being the track on which writing has been performed. As shown in FIG. 4, for example, the erase weights of the tracks (± 1 track) on both sides of the written track are set to “1”, and the other tracks determine the erase weight according to the difference. For example, the erase weight is “0” for ± 4,5 tracks, and “0.9”, “0.5”, “0.5”, “0” is used for ± 2,3 tracks depending on the difference. .2 "erase weight is set.

  In FIG. 4, the erase weight table 52 in the range of ± 5 tracks is shown, but actually, the erase weight table 52 in the range of ± 10 tracks is created from the result of FIG. The erase weight table 52 is stored as an operation parameter in the system area of the magnetic disk, and is read out to the volatile memory 13 when the apparatus is started up.

  Next, the side erase process using the erase weight table 52 will be described with reference to FIG. The side erase management table 56 of FIG. 1 stores each erase point of all tracks. Here, for ease of explanation, a side erase management table 56 in the range of ± 5 tracks is shown.

  In the initial state, the erase point of each track in the side erase management table 56 is “0”. Next, when writing is performed on the track “0” shown in this table, as shown in the side erase management table 56A in FIG. 5, the erase points corresponding to the erase weights in FIG. 4 become erase points for each track. Is added. Here, the erase point of the write target track is cleared to zero.

  Next, when writing is performed on the track “+2” shown in the table 56B, as shown in the side erase management table 56C in FIG. 5, the erase corresponding to the erase weight in FIG. Points are added to the erase point for each track. Here, the erase point of the write target track is cleared to zero. For example, “1.0” which is the weight of the track ± 1 in FIG.

  In this way, the erase point of each track is accumulated with reference to the erase weight table 52 for each write of a certain track. Then, forcible rewrite is performed for a track whose erase point exceeds a specified point (for example, 10,000 points).

  In this manner, the degree of erasure of adjacent tracks when a certain track is continuously written is determined as a weight and stored in the erase weight table 52. Then, when the track is written, the erase weight table 52 is used to accumulate the erase points of each track, and the track position (range) that is equal to or greater than a predetermined threshold is forcibly rewritten.

  For this reason, side erasure can be detected not only for neighboring tracks, but also for tracks with a possibility of far erasure, and only tracks with a possibility of side erasure including far erasure can be determined as rewrite targets. Thereby, unnecessary rewrite can be prevented and it contributes to performance improvement.

  In this case, because of the nature of side erasure, the track position of side erasure including far erasure does not differ so much in each track. For example, measurement is performed on a representative track in one zone, and the relative track from the representative track is measured. It is preferable to register the erase weights in the erase weight table 52 in FIGS.

  Also, the erase amount may differ depending on the temperature. For example, the erase amount tends to be smaller at a low temperature than at a high temperature. For this reason, with respect to the measured erase weight table 52 as shown in FIG. 4, at a high temperature at which the largest erase amount is estimated, the high temperature erase weight is (measured erase weight * 1), as shown in FIG. Set the erase weight as follows.

  Moreover, the erase weights at normal temperature and low temperature are (measured erase weight * 0.8) and (measured erase weight * 0.6), as shown in 52-1 of FIG. 7 and 52-2 of FIG. Set the erase weight. Thereby, useless forced rewrite at normal temperature or low temperature can be reduced.

  Similarly, it is also preferable to determine the erase weight in consideration of the error rate in the initial state. That is, the weight is similarly changed according to the initial error rate. For example, when the initial error rate is standard, the erase weight is the erase weight * 1, and when the initial error rate is poor, the erase weight is 1.5, such as the erase weight * 1.5. Increase For those with a good initial error rate, the erase weight for one write, such as erase weight * 0.8, is reduced.

  As a result, the initial error rate is poor and the relief rate of the magnetic disk device that is erased before the forced rewrite is increased, and a device with a good error rate can reduce unnecessary forced rewrite. .

  The rewrite is performed by reading the data of the track and rewriting the read data on the track.

(Side erase measurement process)
FIG. 9 and FIG. 10 are process flow diagrams of one embodiment of the side erase measurement according to the present invention, and FIG. 11 is an explanatory diagram of the measurement position. This measurement process is performed here in the manufacturing process before product shipment.

  Hereinafter, the measurement process of FIGS. 9 and 10 will be described with reference to FIG.

  (S10) A measurement zone is determined. As shown in FIG. 11, here, the measurement zones are the outer 19-1, the center 19-2, and the inner 19-3 of the magnetic disk 19, one each. First, the MPU 11 in FIG. 1 sets “1” (for example, one zone of the inner 19-3) in the measurement zone Z.

  (S12) Next, the measurement track N is determined. The MPU 11 sets the measurement track number in the measurement track N. For example, the track number of (the innermost track number in the measurement zone−200) is set to the measurement track 0.

  (S14) The MPU 11 measures the error rate in the initial state of the track in the measurement range centered on the measurement track N. Here, as described in FIG. 3, the measurement range is 21 tracks in the range of (N−10) to (N + 10). The error rate is measured by writing data to each track in the measurement range with the magnetic head 25, reading the data of each track a plurality of times (for example, 100 times) with the magnetic head 25, and determining whether a read error has occurred. The number of error occurrences with respect to the number of reads is calculated, and a measured value of the error rate of each track is obtained.

  (S16) Next, the measurement track N is continuously written. That is, the MPU 11 writes data to the magnetic head 25 and to the measurement track N. When writing is performed once, the write count (n) is set to “1”.

  (S18) The MPU 11 refers to the number of writes (n), and determines whether the number of writes has reached a specified number (for example, about 100,000). If the write count has not reached the specified count, the MPU 11 writes data to the measurement track N and increments the write count (n) by “1”.

  (S20) When the MPU 11 determines that the number of writes has reached the specified number, the MPU 11 ends the continuous writing to the measurement track N and starts measuring the error rate. Here, as described in FIG. 3, the measurement range is 21 tracks in the range of (N−10) to (N + 10). The error rate is measured by reading the data of each track a plurality of times (for example, n = 100 times) with the magnetic head 25, determining whether a read error has occurred, calculating the number of occurrences of errors relative to the number of reads, Get a measurement of the error rate.

  (S24) The MPU 11 calculates, for each track, the difference between the initial measurement value in step S14 and the measurement value after the continuous write in step S20.

  (S26) Then, the MPU 11 determines the erase weight of each track from the difference value of each track. For example, the erase weight of the track on both sides of the measurement track N is set to “1.0”, and the other track determines the value obtained by dividing the difference value of each track by the difference value of the tracks on both sides as the erase weight. .

  (S28) The MPU 11 reflects the initial error rate in the determined erase weight. This method is as described above.

  (S30) The MPU 11 determines whether the measurement zone number z is “3”. When the measurement zone number z is “3”, the MPU 11 ends the side erase test.

  (S22) On the other hand, if the measurement zone number z is not “3”, the MPU 11 increments the zone number z by “1” as shown in FIG. 9 and returns to step S12.

  Thus, as shown in FIG. 11, the side erase is performed in one zone of the inner zone (here, zone 8), one zone of the center (here, zone 4), and one zone of the outer zone (here, zone 0). The measurement result is stored in the erase point table 52. The erase point table is stored at a relative track position from the measurement track. Therefore, it can be used in common for each track in the zone. Further, the measurement at each track can be omitted, and the test time can be shortened.

  In other words, the far erase point differs depending on the position of the magnetic disk in the radial direction due to the influence of the yaw angle of the magnetic head. Therefore, the erase point is set for the zone divided in the radial direction of the magnetic disk. In one zone, the erase locations are not so different from each other.

  This side erasure measurement is likely to occur when the write current is set to a high current. Therefore, when the side erasure measurement is performed, the write current is set to a higher value and the measurement can be accelerated. Is possible. In the side erase test process, the degree (weight) of the side erase is measured and registered within the measurement track range, and the erase weight is accumulated when writing a certain track. The accumulated erase point exceeds the specified number of points. Since the track is forcibly rewritten, it is possible to prevent data loss due to side erase including remote erase and to prevent unnecessary track rewrite.

(Light processing)
FIG. 12 is a flowchart of one embodiment of the write processing of the present invention.

  (S40) During operation (read / write) of the apparatus, the MPU 11 monitors commands.

  (S42) Upon receiving the write command, the MPU 11 writes data to the target track of the write command.

  (S44) The MPU 11 reads the weight of the erase weight table 52, and changes it according to the temperature at the time of writing, as described in FIGS. Then, the erase weight is added to the corresponding track column of the side erase management table 56 described with reference to FIG.

  (S46) The MPU 11 determines whether or not there is a track having a cumulative erase point in the side erase management table 56 equal to or greater than a specified point (for example, 10,000 points). If the MPU 11 determines that there are no tracks in the side erase management table 56 that are cumulative erase points equal to or greater than the specified point, the process returns to step S42.

  (S48) When the MPU 11 determines that there is a track that is a cumulative erase point greater than or equal to the specified point in the side erase management table 56, the MPU 11 forcibly rewrites a track that has an erase point greater than or equal to the specified point. That is, the data of the track is read by the magnetic head 25, and the read data is rewritten to the read track. Then, the process returns to step S40.

  In this way, in the side erase test process, the degree (weight) of side erasure is measured and registered within the measurement track range, and the erase weight is accumulated when a track is written, and the accumulated erase point is defined. When the number of points is exceeded, the track is forcibly rewritten, so that it is possible to prevent data loss due to side erase including remote erase and to prevent unnecessary track rewrite.

(Other embodiments)
In the above-described embodiment, the side erase locations are measured and stored in each zone. However, one side erase location may be measured and stored on one surface of the magnetic disk, that is, one on the magnetic head. . A plurality of erase weight tables may be provided such as high temperature, normal temperature, and low temperature. Further, although the data storage device has been described as a magnetic disk device, the present invention can also be applied to a data storage device using another storage medium such as an optical disk or a magneto-optical disk. The interface is not limited to SATA, and can be applied to other interfaces.

  As mentioned above, although this invention was demonstrated by embodiment, in the range of the meaning of this invention, this invention can be variously deformed, These are not excluded from the scope of the present invention.

(Appendix 1)
A head for reading and writing data to a storage medium; an actuator for moving the head to an arbitrary track of the storage medium; and an initially measured error rate for each track in a predetermined range centered on the track to be measured The erase weight of each track determined by the measured error rate and difference of each track in a predetermined range centered on the track to be measured after writing the track to be measured by the head a predetermined number of times is stored. The erase weight table, the side erase management table for storing the erase point of each track, and when the desired track is written, the erase weight table is referred to, and the erase point of the corresponding track in the side erase management table is accumulated. And from the side erase management table A control circuit for determining that there is a track having an erase point number equal to or greater than a specified number of points, and forcing a retry to read and rewrite data of the track determined to exist by the head. A data storage device.

(Appendix 2)
The data storage device according to appendix 1, wherein the erase weight table stores an erase weight at a relative position of each track around the measurement target track.

(Appendix 3)
When the desired track is written, the control circuit refers to the erase weight table and accumulates erase points of the corresponding track in the side erase management table with an erase weight corresponding to a device temperature. The data storage device according to appendix 1.

(Appendix 4)
The control circuit refers to the erase weight table when writing the desired track, and sets the erase point of the corresponding track in the side erase management table with an erase weight corresponding to the initial error rate of each track. The data storage device according to appendix 1, characterized by being accumulated.

(Appendix 5)
The control circuit measures the initial error rate of each track in a predetermined range centered on the measurement target track, and then centers the measurement target track after writing the measurement target track a predetermined number of times by the head. The data storage device according to appendix 1, wherein an error rate of each track in a predetermined range is measured, an erase weight of each track is determined based on a difference between the two error rates, and the erase weight table is created.

(Appendix 6)
In the erase weight table, the erase weight of each track obtained by measuring the storage medium by continuous writing in the predetermined track of the predetermined zone among the plurality of zones divided in the radial direction, The data storage device according to appendix 1, wherein the data storage device is stored.

(Appendix 7)
In the erase weight table, the erase weight of each track obtained by measuring the storage medium by continuous writing of the predetermined track in a representative zone among a plurality of zones divided in the radial direction is calculated for each zone. The data storage device according to appendix 6, wherein the data storage device is stored.

(Appendix 8)
The data storage device according to appendix 1, wherein the storage medium is formed of a magnetic disk, and the head is formed of a magnetic head.

  In the side erase test process, the degree (weight) of the side erase is measured and registered within the measurement track range, and the erase weight is accumulated when writing a certain track. The accumulated erase point exceeds the specified number of points. Since the track is forcibly rewritten, it is possible to prevent data loss due to side erase including remote erase and to prevent unnecessary track rewrite.

10 disk device 11 MPU (processing unit)
16 HDC
13 Volatile memory (RAM)
14 Data buffer 15 Data buffer control circuit 24 Read channel circuit 19 Bus 18 Head IC
19 Storage media (magnetic disk)
20 Spindle motor 22 Actuator (VCM)
25 head (magnetic head)
52 Erase Weight Table 56 Side Erase Management Table

Claims (5)

A head for reading and writing data to a storage medium;
An actuator for moving the head to an arbitrary track of the storage medium;
Initially, the measured error rate of each track in a predetermined range centered on the measurement target track, and each of the predetermined range centered on the measurement target track after writing the measurement target track a predetermined number of times by the head An erase weight table that stores the erase weight of each track determined by the measured error rate and difference of the track;
Side erase management table that stores the erase points for each track;
When a desired track is written, the erase weight table is referred to, the erase points of the corresponding track in the side erase management table are accumulated, and the number of erase points from the side erase management table is equal to or greater than the specified number of points. A data storage device, comprising: a control circuit that determines that a certain track exists, reads out data of the track determined to be present by the head, and executes a forced retry for rewriting. The data storage device according to claim 1, wherein the erase weight table stores an erase weight at a relative position of each track centered on the measurement target track. When the desired track is written, the control circuit refers to the erase weight table, and accumulates erase points of the corresponding track in the side erase management table with an erase weight corresponding to a device temperature. The data storage device of claim 1. The control circuit refers to the erase weight table when writing the desired track, and sets the erase point of the corresponding track in the side erase management table with an erase weight corresponding to the initial error rate of each track. The data storage device according to claim 1, wherein the data storage device is accumulated. The control circuit measures the initial error rate of each track in a predetermined range centered on the measurement target track, and then centers the measurement target track after writing the measurement target track a predetermined number of times by the head. The data storage device according to claim 1, wherein an error rate of each track in a predetermined range is measured, an erase weight of each track is determined based on a difference between the two error rates, and the erase weight table is created.

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