JP2000243049A - Seek error preventing method for magnetic disk device, magnetic disk device, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect external noise and fine Barkhausen noise and to prevent seek error by providing the prescribed cylinder on a magnetic disk, starting seek error detection prevention control when a command is not inputted for a fixed time or more, and performing dummy-write or head change operation when a seek error is detected. SOLUTION: When it is detected that a command is not generated for a fixed time in an idle time detecting section 10, a seek error detection preventing section 2 is started, operation seeking the prescribed cylinder is started, and it is discriminated whether positioning is performed for a cylinder specified by a seek error discriminating means 12b or not. When a seek error is detected, one side or both sides of dummy-write and head change are performed and Barkhausen noise is eliminated, and corresponding head number and the like are recorded in log information. In operation by the seek error detection preventing section 12, a head is switched successively and it is repeatedly performed for each head while an idle time is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preventing a seek error in a magnetic disk drive, a magnetic disk drive, and a recording medium.

In the embedded servo system of a magnetic disk drive, unlike a servo surface servo system in which only servo information is stored, servo information is embedded (embedded) in a surface for storing data. The head was positioned by reading. Also, instead of a conventional ferrite type head, an MR head is used as a head for writing and reading data on and from a magnetic disk at high density.
(Magneto Resistive: magnetoresistive effect) Heads have come to be used, but since they are susceptible to noise, improvement is desired.

[0003]

2. Description of the Related Art FIG. 5 shows a magnetic disk of an embedded servo. Servo information is recorded on the magnetic disk at regular intervals on each track, and a servo area is provided in a data surface in a fan shape. The structure of the servo information is shown in FIG. 6, in which a servo mark on which data indicating servo information is recorded is first placed, then a position signal for detecting and correcting a head position shift, and then a cylinder number. , Head number information is recorded in gray code. This gray code can be read even when the head crosses a part of the data when the head is not always located at the center of the data. The data head synchronizes with the servo information by detecting the servo mark, and reads the subsequent position information, gray code, and the like.

In this embedded servo system, unlike the conventional servo surface servo, offset correction for data is performed in real time, so that positioning accuracy during seek (or tracking) operation can be increased,
It has become possible to increase the recording density.

At present, an MR head capable of dramatically increasing the recording density of a conventional ferrite is used as a data head. In the MR head, the resistance value changes in response to a change in magnetic flux, and when a current flows through the MR head, a voltage corresponding to the resistance value changes, and the voltage is obtained as a reproduction output. Therefore, the MR head is easily affected by the output voltage due to external noise. If the magnetic domains of the MR head are aligned, there is no problem. However, if the magnetic domains are not aligned due to poor characteristics at the time of manufacture, or if the magnetic domains are disturbed (unaligned) during use, the reproduced signal is Noise occurs. This phenomenon is called Barkhausen noise.

When such noise occurs, data cannot be read from the magnetic disk, and servo information cannot be read. Therefore, a seek (tracking) error occurs. Therefore, the following method has conventionally been used to remove extraneous noise and Barkhausen noise.

That is, if Barkhausen noise occurs at the time of reading, an error occurs at the time of seeking.
Disturbance is caused by a method such as writing data at the time of a seek retry (retrying the seek operation) or performing a head change (by switching the head to the spare, the bias current is momentarily extinguished). There is a high probability that the magnetic domains are uniform and no noise is generated.

Therefore, a method of removing Barkhausen noise by performing a dummy write (writing dummy data) or performing a head change during a seek retry has conventionally been adopted.

[0009]

However, the method of dummy write or head change is not a method that can always remove Barkhausen noise by performing it once. Detects and takes countermeasures such as dummy write and head change if necessary, or when SMART data (a seek error or write error rate specified by SCSI, which is one of the interface standards, exceeds a certain level). There is a demand for a method of recording a log in, for example, data used to generate an alarm indicating a prediction of a failure.

If Barkhausen noise is severely generated, an error occurs at the time of seek, so that a method of removing Barkhausen noise by performing dummy write or head change at the time of seek retry may be performed.

However, in the case of slight Barkhausen noise, an error does not occur at the time of seeking and the head is often detected after the head is read after on-track. In this case, a method for removing Barkhausen noise such as a dummy light was not applied, or the application was delayed.

[0012] Further, if the device becomes defective due to extraneous noise or Barkhausen noise after the device is shipped, the same state is not always reproduced even if the cause is investigated afterwards.
It is often difficult to identify the cause.

It is an object of the present invention to provide a method for preventing a seek error of a magnetic disk drive, a magnetic disk drive, and a computer-readable recording medium capable of detecting a foreign noise or a slight Barkhausen noise to prevent a seek error. Aim.

[0014]

FIG. 1 shows the principle of the present invention.

In FIG. 1, 1 is a control unit of the magnetic disk drive, 10 is an idle time detecting unit, 11 is a command detecting unit, and 12 is a command detecting unit.
Is a seek error detection prevention unit, 12a is a specific cylinder seek unit, 12b is a seek error discriminating unit, 12c is a Barkhausen noise removing unit, and 12d is a log recording unit.

According to the present invention, a specific cylinder (specific, same track on all data surfaces) in which recording of servo information is sufficiently provided on a magnetic disk is provided. Similar servo information may be used, and at the time of a process test before shipment, each servo information of this specific cylinder may be read by a test command or the like to ensure that the recording medium has no defect and is normal data.

During operation of the magnetic disk drive, when the controller 1 of the magnetic disk drive detects that no command is generated for a predetermined time in the idle time detector 10, the seek error detection prevention unit 12 is activated. When activated, the seek error detection prevention unit 12 starts the operation of seeking the specific cylinder described above, and determines whether or not the seek cylinder is positioned at the designated cylinder by the seek error determination means 12b (whether a seek error is not detected). If a seek error is not detected, the operation of the seek error detection prevention unit 12 ends. However, if a seek error is detected, the write information of the specific cylinder is sufficiently assured. Since there is a high probability that noise irrelevant to the medium to be generated occurs, a method for removing Barkhausen noise is performed. That is, one or both of the dummy write and the head change are executed. After this,
The corresponding head number or the like is recorded in log information. The operation by the seek error detection prevention unit 12 is repeatedly performed for each head by sequentially switching the heads (each disk surface) while the idle time continues. The log information is used for preventive maintenance and investigation of a failure that occurs later.

Although the control section of the magnetic disk drive is shown in FIG. 1 as hardware means, it is clear that the control section can be realized by software, and it is shown as a configuration of an embodiment described later. In addition, such software (program) can be stored in a computer-readable recording medium and loaded into a necessary device for execution.

[0019]

FIG. 2 shows a hardware configuration of a magnetic disk drive according to the present invention. In FIG.
20 is a magnetic disk, 21 is a micro control unit (MCU) for controlling the entire magnetic disk device, 2
Reference numeral 2 denotes a flash ROM that holds a program for performing a boot operation when the power of the magnetic disk device is turned on.
M: rewritable nonvolatile memory), 23 is a RAM storing a control program including a program for performing a process for detecting and preventing a seek error according to the present invention, 24 is a hard disk controller (HDC), and 25 is a read (read). / A data buffer for temporarily storing write data; 26, a drive interface for controlling a head driver, a servo information channel, and an interface with a data signal channel; and 27, for controlling a mechanical system. A digital signal processor (Digital Signal Processor) for performing signal processing, 28 is a servo driver for driving the positioning of the head, 29 is a servo channel which is a circuit for reading and writing signals of servo information, and 30 is for reading and writing data signals. Read channel (READ CHANN EL).

In the configuration shown in FIG. 2, the hard disk controller (HDC) 24 communicates with an upper-level host (computer) and a SCSIif (Small Computer System Interface).
e), and receives a command (read, write, etc.) from the host and instructs the MCU 21, and write data and read data are input / output via the data buffer 25.

FIG. 3 is a flowchart of the embodiment. This flowchart is executed according to a program (stored in the RAM) in the micro control unit (MCU) in the hardware configuration of FIG. In the case of this magnetic disk device, it is assumed that the recording of servo information is sufficiently guaranteed on the cylinder A of the magnetic disk in advance.

The MCU periodically determines whether it has received a command (various types such as read and write) from the host (S1 in FIG. 3), and executes the command if received (S2 in FIG. 3). If the command is not received, the time is counted and it is determined whether or not a predetermined time or more has elapsed (S3 in FIG. 3). If not, the process returns to the first process (S1 in FIG. 3). If so, seek to cylinder A (S4). At this time, it is determined whether a seek error (tracking error) has occurred (S5 in FIG. 3).
When a seek error is detected, it is determined whether a predetermined number of occurrences of the seek error has been exceeded (S in FIG. 3).
6) If the error has repeatedly occurred and the specified number of times has been exceeded, log information is recorded by the route (see S
15), seek error detection operation on the path (S5)
Move to If the number of times does not exceed the specified number, dummy write is performed at the time of seek retry as in the past (S
A head change is performed together with 7) (S8), and an attempt is made to remove Barkhausen noise. Thereafter, the operation shifts to a seek error detection operation through the following path.

In the above step S5, if the on-track operation is normally performed without detecting a seek error (S9 in FIG. 3), a tracking error (for example, at least a time required for one round of the track) within a prescribed time period. , Servo mark not found, etc.) are monitored (S10). If no servo error is detected within the specified time, it is determined whether or not the seek operation of the cylinder A has been completed for all the heads (S11 in FIG. 3). If not, a head change is performed (S8 in the same manner). The seek of the cylinder A is performed for the head (S5).

If a servo error occurs within the specified time in step S10, it is highly possible that the error is Barkhausen noise. Therefore, dummy write or head change is performed (S12 in FIG. 3), and seek recovery is performed. In step S13, it is determined whether the number of times has exceeded the specified number of times (step S14). If the number of times has not exceeded the limit, the process returns to the seek operation of the cylinder A, on-track again, and it is monitored whether a servo error occurs. In the invention IPL in which a servo error occurs even if this operation is repeated a predetermined number of times, the head is recorded in log information such as SMART, the head is changed, and the same operation is performed.

When a tracking error is detected after on-track, a medium flaw or thermal aspirity (MR) is detected.
It is better to detect noise generated by the thermal characteristics of the head, perform seek recovery, and then verify whether the noise occurs in the same frame.

The above operation must be interrupted immediately upon receipt of a command, reset, abort, etc., in order to prevent a timeout detected by the host.

The program for performing the processing according to the flowchart shown in FIG. 3 can be executed in an information processing system that executes the program shown in FIG.

In FIG. 4, reference numeral 30 denotes a processing unit, and 31 denotes a memory in which programs and data such as a RAM or a hard disk in the processing unit are loaded. 32
Is a memory (for example, DASD or the like) storing a program of a remote device provided by a program provider connected to the processing device 30 via a line, and 33 is a CD-ROM or a flexible disk storing a program (data).
The recording medium according to the present invention comprises:
-It can be recorded on any of various forms of recording media such as a ROM or a flexible disk 33 or the memory 31 of the processing device 30, and is loaded into the memory of the processing device 30 and executed.

[0029]

According to the present invention, the dummy write and the head change are the methods which are effective for Barkhausen noise, but are not a method for surely removing the noise. Therefore, as described above, Barkhausen noise is monitored when a command is not received, and if occurrence is confirmed, Barkhausen noise is removed as much as possible, thereby reducing the probability of occurrence of Barkhausen noise during command execution. Can be.

Further, by recording the log information, a magnetic disk device having a very high frequency of occurrence of Barkhausen noise can be replaced at an early stage. Furthermore, after the Barkhausen noise occurs temporarily, it often does not reappear when the power is turned off and on. In many cases, the cause of the failure cannot be determined in a subsequent fault investigation. Can be useful for investigations.

In the present invention, there is no need to write a special pattern on the cylinder to detect noise.
No special detection circuit is required, and it can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention.

FIG. 2 is a diagram illustrating a hardware configuration of a magnetic disk drive in which the present invention is implemented.

FIG. 3 is a diagram showing a processing flow of the embodiment.

FIG. 4 is a diagram illustrating an information processing system that executes a program.

FIG. 5 is a diagram showing a magnetic disk of an embedded servo.

FIG. 6 is a diagram showing a configuration of servo information.

DESCRIPTION OF SYMBOLS 1 Control unit of magnetic disk drive 10 Free time detection unit 11 Command detection unit 12 Seek error detection prevention unit 12a Specific cylinder seek unit 12b Seek error determination unit 12c Barkhausen noise removal unit 12d Log recording unit

Claims (4)

[Claims] In a method for preventing a seek error of a magnetic disk drive, a specific cylinder in which recording of servo information is sufficiently guaranteed is provided on a magnetic disk so that no command is input for a certain period of time during operation of the magnetic disk drive. Then, the control for seek error detection prevention is activated, the specific cylinder is sought by the activation to detect the presence or absence of a seek error, and when a seek error is detected, any one of dummy write and head change is executed. A method for preventing a seek error in a magnetic disk drive, wherein the same processing is repeated for the next head when the processing is completed for one head. 2. The method according to claim 1, wherein when the occurrence of the seek error is detected, related information including head information is stored as log information. 3. A magnetic disk drive, wherein a specific cylinder on which recording of servo information is sufficiently guaranteed is provided on a magnetic disk, and the magnetic disk drive detects an idle time during which no command is input for a predetermined time or more during operation. And a seek error detection / prevention unit that is activated when the detection unit detects an idle time. The seek error detection / prevention unit includes a unit that seeks the specific cylinder when the unit is activated, and a seek error detection unit that activates a seek error. When seek error determining means for determining whether or not an error has occurred, and when the occurrence of an error by the seek error determining means has been determined,
A barkhausen noise removing unit for performing any one of a dummy write operation and a head change operation, wherein the seek error detection prevention unit repeatedly controls each head for each head while the idle time continues. Magnetic disk device. 4. A computer-readable recording medium for controlling a magnetic disk device provided with a specific cylinder on which recording of servo information is sufficiently guaranteed on a magnetic disk, wherein the recording medium is fixed during operation of the magnetic disk device. When an empty state where no command is input for a longer time is activated, control for preventing a seek error detection is started, the specific cylinder is sought to detect the presence or absence of a seek error, and one of a dummy write and a head change is detected by detecting the seek error. A computer-readable recording medium on which is recorded a program for executing one operation and repeatedly executing the same processing for each head during the idle state.