JP2511723B2 - Testing method of data destruction difficulty in magnetic disk drive - Google Patents

Description

The present invention relates to a method for testing whether or not a magnetic disk medium, which is a magnetic recording medium, easily causes data destruction in a magnetic disk device used as a file device of a computer system. The purpose of the present invention is to realize a highly reliable magnetic disk device that does not cause data destruction by making it possible to perform a pressure demagnetization test on all the disk media. The test data signal is written in the zone, secondly, the test data signal of the previously written CSS zone is read, thirdly, the CSS of the magnetic disk device is performed plural times, and fourthly, the CSS after the CSS operation is performed.
By reading the test data signal in the S zone and comparing the second test data read signal with the fourth test data read signal, it is possible to test whether or not the magnetic disk medium is likely to cause data destruction. Configure.

[Industrial applications]

The present invention relates to a method for testing whether a magnetic disk medium, which is a magnetic recording medium, is likely to cause data destruction in a magnetic disk device used as a file device of a computer system.

A magnetic disk device is a magnetic disk medium that rotates,
Data is magnetically recorded (write / write via a magnetic head).
It is a device for reading).

Therefore, it is important to maintain the recorded data in a stable manner in order to ensure the reliability of the magnetic disk device.

On the other hand, there is a demand for a magnetic disk device that is small in size and has a large storage capacity, and it is more important to secure the reliability in the demand.

On the other hand, in order to realize the small size and large storage capacity of the magnetic disk device, it is necessary to increase the recording density on the magnetic disk medium, and accordingly, the flying height of the magnetic head must be decreased.

However, the decrease in the flying height of the magnetic head makes it easier for the magnetic disk medium and the magnetic head to come into contact and collide with each other, which causes the recorded data to be destroyed. Therefore, measures are taken to ensure the flying stability of the magnetic head. The data destruction may be caused by pressure demagnetization or damage of the magnetic disk medium.

However, when comparing the individual magnetic disk media, there are some deviations in their characteristics and qualities, which is a potential factor for the occurrence of the data destruction.

Therefore, there is a demand for a test method for detecting the potential cause of the data destruction before shipping the magnetic disk device and eliminating it beforehand.

[Conventional technology]

(1) Pressurized demagnetization and data destruction due to damage 1) Pressurized demagnetization When a rotating magnetic disk medium comes into contact with a magnetic head or the like and receives pressure, the strength of the recording magnetic field at the contact portion decreases. . That is, this is pressure demagnetization.

The pressure demagnetization occurs because the magnetic body is distorted by the pressure when the magnetic head comes into contact with the magnetic head, and also due to the heat generated during the contact.

That is, the cause is that a chemical change occurs in the magnetic substance due to the contact of the magnetic head.

Then, demagnetization has a possibility of destroying recorded data.

2) Damage When a magnetic head or the like comes into contact with a rotating magnetic disk medium, the magnetic film of the magnetic disk medium may be damaged.

Since the damage occurs in the magnetic film itself holding the recorded data, it becomes a cause of destroying the recorded data.

(2) Method of Testing Magnetic Disk Medium Damage to the magnetic disk medium can be almost solved by improving the protective film of the magnetic disk medium and using a lubricant. Of course, we are also taking measures to improve the floating stability of the magnetic head.

However, with regard to pressure demagnetization, even a magnetic disk medium manufactured through the same manufacturing process has some deviation, which is a potential instability factor against data destruction. There is.

Therefore, a pressure demagnetization sampling test is performed for each manufacturing lot of magnetic disk media. The sampling test of the magnetic disk medium is performed individually for each medium.

FIG. 4 is a block diagram illustrating a method for measuring pressure demagnetization.

That is, the demagnetization amount is measured and tested according to the following procedure.

The magnetic disk medium 1 is rotated, and the test apparatus 4 records a test data signal on the magnetic disk medium 1 via the magnetic head 3.

The test data signal is read by the magnetic head 3, and the magnitude of the output voltage is measured by the test device 4 and stored.

The magnetic head 1 for pressurizing the slider so that the slider width of the magnetic head is narrowed so that the magnetic head hardly floats.
Then, the test data signal is contacted and slid at the track position where the test data signal is recorded.

Once again, the test data signal is transferred to the magnetic head 3
Is read out, the magnitude of the output voltage is measured by the test apparatus 4 and stored.

From the amount of decrease in the measured voltage with respect to the measured voltage, the demagnetization amount of the magnetic disk medium 1 due to pressurization is obtained.

 The above is the procedure.

By the way, the reason why the measurement of the demagnetization amount is a sampling test is that the contact and sliding of the pressurizing head 5 damages the surface of the magnetic disk medium 1.
That is, the magnetic disk medium 1 after the inspection cannot be incorporated in the magnetic disk device.

[Problems to be Solved by the Invention]

However, the conventional test method has the following problems.

1) The magnetic disk medium 1 is damaged by the contact and sliding of the pressing magnetic head 5.

Therefore, the test cannot be performed on all the magnetic disk media.

2) In the sampling test for the reason 1), the demagnetization amount can be known for each manufacturing lot of the magnetic disk medium, but the demagnetization amount for each magnetic disk medium cannot be known.

That is the problem. Therefore, even if the result of the sampling test is good, the magnetic disk device incorporating the magnetic disk medium causes pressure demagnetization in the market,
It may cause a system down of the computer system.

The technical problem of the present invention is to solve the above problems in the conventional magnetic disk device and to perform the pressure demagnetization test on all the magnetic disk media, thereby ensuring reliability without data destruction. To realize a highly reliable magnetic disk device.

[Means for solving the problem]

FIG. 1 is a diagram for explaining the basic principle of the present invention.
Is a block diagram for testing a magnetic disk device,
(B) is a flowchart explaining a test method (test procedure) by data comparison, (c) is a flow chart explaining a test method (test procedure) by signal amplitude comparison.

The present invention is characterized in that at the stage of a magnetic disk device incorporating a magnetic disk medium, a test data signal is written in the CSS zone to test the magnetic disk medium.

(1) Basic Test Method (Test Procedure) That is, in the magnetic disk device 6, firstly, a test data signal is written in the CSS (CONTACT START STOP) zone 10.

Second, the previously written CSS zone test data signal is read.

Thirdly, CSS (CONTACT START S
TOP) multiple times.

Fourth, the test data signal in the CSS zone after the CSS operation is read again.

Then, by comparing the second test data read signal and the fourth test data read signal, it is a method of testing whether or not the magnetic disk medium 1a is likely to cause data destruction.

(2) Method of comparing test data read signals In the basic test method of (1), there are the following two methods of comparing test data read signals.

1) A method of performing data comparison.

2) Method by comparing signal amplitudes.

(3) Identification of defects generated after CSS of magnetic disk device When a defect of a magnetic disk medium newly generated after CSS is recognized by comparing test data read signals according to 1) and 2) of (2) above, To identify defects, the test is performed according to the following procedure.

First, rewrite the test data signal in the CSS zone.

Secondly, the rewritten CSS zone test data signal is read again.

When the second test data read signal still has the defect, it can be determined by CSS of the magnetic disk device that a permanent defect has occurred in the magnetic disk medium 1a.

Further, when the second test data read signal has no defect, it is caused by pressure demagnetization.
Magnetic disk media with low reproducibility and unstable data destruction
It can be judged that 1a is likely to occur.

[Operation] During the period from the stopped state of the magnetic disk medium 1a to the constant speed rotation state, or from the constant speed rotation state to the stop, the CS of the magnetic disk medium 1a is
The magnetic head 3a contacts and slides in the S zone.

Therefore, when the data is recorded in the CSS zone and the CSS of the magnetic disk device 6 is repeatedly performed, the data recorded in the CSS zone of the magnetic disk medium 1a is placed in the most severe environment. Therefore, no data is recorded in the CSS zone.

According to the present invention, a test data signal is written in a CSS zone in which data is not conventionally recorded, and the magnetic disk medium 1a
The test for the data destruction of

The test method of the present invention does not damage the magnetic disk device 6 at all, only by writing the test data signal in the CSS zone. Therefore, it is possible to perform a test on all the magnetic disk devices.

(1) Comparison of basic test method and test data read signal CSS of the magnetic disk device 6 is the magnetic disk device 6
It is most suitable for measuring the resistance to data destruction for the test data signal written in the CSS zone.

Therefore, the test data signal written before CSS and C
By comparing the test data signal read after SS and observing the difference, the state of data destruction can be known.

On the other hand, the comparison of the test data read signal before and after CSS is
The difference can be observed by digitally comparing the data. The difference can also be observed by comparing the signal amplitudes in an analog manner. It should be noted that it does not hinder the combined use of both.

If the test data read signals before and after CSS match, it can be determined that the magnetic disk medium 1a has no defect that causes data destruction.

(2) Identification of defects generated after CSS of magnetic disk device In the above (1), if the test data read signals before and after CSS of the magnetic disk device 6 do not match, the CS
Due to S, the magnetic disk medium 1a has a defect that causes data destruction.

Then, in order to identify the defect, CSS is used again.
Rewrite the test data signal to the zone, then CS
It is possible to read the test data signal of the S zone again.

That is, if the read-out signal still has a mismatch, it means that a permanent defect such as damage has occurred at the mismatched portion of the magnetic disk medium 1a.
If the inconsistency disappears and the original state is restored, it means that the magnetic disk medium 1a has an unstable defect with low reproducibility due to pressure demagnetization.

〔Example〕

An example of how the test method for data destruction in the magnetic disk device according to the present invention can be actually embodied will be described.

(1) Configuration The hardware configuration for testing can be the same as before. By the way, the block diagram that can be described most simply is the same as FIG. 1 (a).

However, the conventional magnetic disk device 6 and test device 4a
In the above, the control units of both devices prohibit writing / reading of data to / from the CSS zone.

Therefore, the software of the control unit is changed so that data can be written / read to / from the CSS zone only during the test.

(2) Test Method-1 FIG. 2 is a diagram for explaining Example-1, (a) is a flowchart for explaining the test procedure, (b) is an observed waveform diagram of an error portion, and (c) is an error waveform. It is the observed waveform diagram which was restored. In addition, in the waveform diagrams of (b) and (c), the portion shown by the band of vertical lines indicates that it is observed as a band of bright lines on the oscilloscope.

 Next, the test procedure will be described step by step.

CSS zone, for example CYL (CYLINDER) No.1372,1374,1
A test data signal is written in 376 and 1378 at a frequency 3/4 times the normal write frequency.

The write frequency and the data pattern may be selected and determined according to the magnetic disk device that is the device under test.

The error detection level of the test equipment is set to MIS (MISSINGLEVE
L) 60%, NM (NEGATVE MODULATION LEVEL) 70%, P
Set M (POSITIVE MODULATION LEVEL) to 130% and C
Read the test data signal in the SS zone, measure and store each error condition.

Perform CSS of the magnetic disk unit 40 times. The number of CSSs may be selected and determined according to the magnetic disk device.

Aging is performed by setting the internal temperature of the magnetic disk device to 40 ° C.

Test equipment error detection level: MIS 60%, NM 7
Set 0% and PM to 130%, read the CSS zone test data signal again, measure and store each error condition.

The error occurrence status is compared with the error occurrence status to check whether or not a new error has occurred after CSS.

If no new error has occurred, it can be determined that the magnetic disk medium of the magnetic disk device under test does not have a defect associated with pressure demagnetization that causes data destruction.

Further, when a new error has occurred, it can be determined that there is a defect that causes data destruction.

In the above, when a new error has occurred, the test data read signal at the error location (defective location) is observed as a waveform and the waveform is recorded.

The waveform is recorded by using a photograph or a digital storage type oscilloscope.

Incidentally, FIG. 2 (b) is an example of the observed waveform,
An error has occurred in the amplitude lowering unit 12.

The same test data signal as the test data signal written in the above is written again in the CSS zone.

The test data read signal of the portion (defect portion) where the waveform is observed in the above is observed again and recorded.

Then, as a result, if the amplitude lowering section 12 of the observed waveform recorded above has returned to the normal amplitude, the magnetic disk medium of the magnetic disk device under test shows reproducibility due to pressure demagnetization. It can be determined that there are low, unstable defects.

If the amplitude reduction unit 12 can still be confirmed,
It can be judged that there is a permanent defect due to damage or the like.

By the way, FIG. 2 (c) shows an example of the observed waveform when the amplitude is restored.

(3) Test method-2 FIG. 3 is a diagram for explaining the example-2, (a) is a flowchart for explaining the test procedure, (b) is an observed waveform diagram of an error portion, and (c) is an error waveform. It is the observed waveform diagram which was restored. In addition, in the waveform diagrams of (b) and (c), the portion shown by the band of vertical lines indicates that it is observed as a band of bright lines on the oscilloscope.

 Next, the test procedure will be described step by step.

CSS zone, e.g. CYL No.1372,1374,1376,1378
Then, write the test data signal at a frequency 3/4 times the normal write frequency.

The test data signal in the CSS zone is read out, and the amplitude of the read out signal is measured and stored at a predetermined amplitude, that is, at a slice level (SLICE LEVEL) Ls or less, that is, at an error position.

 Perform CSS of the magnetic disk unit 40 times.

Aging is performed by setting the internal temperature of the magnetic disk device to 40 ° C.

The test data signal in the CSS zone is read again, and a portion where the amplitude of the read signal is equal to or lower than the slice level Ls, that is, an error portion is measured and stored.

The error occurrence location is compared with the error occurrence location to check whether a new error location has occurred after CSS.

If no new error location has occurred, it can be determined that the magnetic disk medium of the magnetic disk device under test does not have a defect associated with demagnetization under pressure that causes data destruction.

When a new error location has occurred, it can be determined that there is a defect that causes data destruction.

In the above, when a new error has occurred, the test data read signal at the error location (defective location) is observed as a waveform and the waveform is recorded.

The waveform is recorded by using a photograph or a digital storage type oscilloscope.

Incidentally, FIG. 3 (b) is an example of the observed waveform,
The amplitude is reduced in the error parts 13a and 13b, and is below the slice level Ls.

The same test data signal as the test data signal written in the above is written again in the CSS zone.

The test data read signal of the portion (defect portion) where the waveform is observed in the above is observed again and recorded.

As a result, if the error portions 13a, 13b of the observed waveform recorded above have returned to the normal amplitude, the magnetic disk medium of the magnetic disk device under test is reproducible due to pressure demagnetization. It can be judged that there is an unstable defect having a low value.

If the error portions 13a and 13b can still be confirmed, it can be determined that a permanent defect due to damage or the like exists.

Incidentally, FIG. 3C shows an example of an observed waveform when the amplitude is restored.

(4) Positioning in the manufacturing process of the magnetic disk device The test method of this embodiment has very good compatibility with the manufacturing process currently performed. That is, the inspection process after the assembly of the magnetic disk device is completed can be carried out without modification.

 Next, a certain example will be described in a fragmentary manner.

(From the previous process) CSS test The familiarity between the magnetic disk medium and the magnetic head is tested.

 Aging Performs a running test of the magnetic disk unit.

Media test Tests that writing / reading of magnetic disk media in the DATA zone is performed correctly.

Off-Track Test Test how much off-track is caused by the aging.

(To the next step) The inspection is performed as described above.

Therefore, before the CSS test step, a test data signal may be written in the CSS zone to compare the test data signal before and after the CSS test. Also, the comparison of the test data signals can be performed in the above-mentioned medium testing process.

Therefore, even if this embodiment is incorporated into the manufacturing process, the time required to inspect the magnetic disk device hardly increases.

(5) Implementation Results As a result of actually performing this Example-1 (Test Method-1),
The error injury rate was about 1/7, and extremely high reliability could be obtained.

〔The invention's effect〕

As described above, according to the present invention, at the stage of a magnetic disk device incorporating a magnetic disk medium, a test data signal is written in the CSS zone, and a test for a potential factor that causes data destruction, in particular, pressure demagnetization is performed. You can Moreover, the time required for the test hardly increases.

As a result, it becomes possible to perform a pressure demagnetization test on all magnetic disk media, and no data destruction occurs.
A highly reliable magnetic disk device can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic principle of the present invention, (a) is a block diagram for testing a magnetic disk device, and (b) is a diagram.
Is a flow chart for explaining a test method (test procedure) by data comparison, (c) is a flow chart for explaining a test method (test procedure) by comparison of signal amplitudes, and FIG. 2 is a view for explaining Example-1. (A) is a flow chart explaining the test procedure, (b) is an observed waveform diagram of an error location, (c) is an observed waveform diagram in which the error is recovered, and FIG. 3 is a diagram for explaining Example-2. (a) is a flowchart explaining the test procedure, (b) is an observed waveform diagram of an error location, (c) is an observed waveform diagram in which the error is recovered, and FIG. 4 is a block diagram illustrating a method for measuring pressurization demagnetization. ,
Is. In the figure, 1 and 1a are magnetic disk media, 2 is a center point, and 3,
3a is a magnetic head, 4 and 4a are test devices, 5 is a pressure head,
6 is a magnetic disk device, 7 is a spindle motor, 8 is an actuator motor, 9 is a carriage, 10 is a CSS zone, 11 is a DATA zone, 12 is an amplitude lowering part, 13a and 13b are error parts (amplitude lowering part), and 14 is The spindle is shown respectively.

Claims (5)

(57) [Claims] 1. A method for testing whether or not a magnetic disk medium (1a) is apt to cause data destruction in a magnetic disk device (6), and firstly, a CSS (CONTACT START STOP) zone ( 10) Write the test data signal to the second, read the test data signal of the CSS zone written previously, and third, CSS (CONTACT START) of the magnetic disk device (6).
STOP) multiple times, and fourth, by reading the test data signal in the CSS zone after the CSS operation and comparing the second test data read signal with the fourth test data read signal, A method of testing the degree of difficulty of data destruction in a magnetic disk device, which comprises testing whether or not the magnetic disk medium (1a) easily causes data destruction. 2. A test method of data destruction difficulty in a magnetic disk device, wherein the comparison of the test data read signals according to claim 1 is performed by data comparison (DATA COMPARE). 3. A test method of data destruction difficulty in a magnetic disk device, wherein the test data read signals according to claim 1 are compared by comparing signal amplitudes. 4. The test method for data destruction difficulty in a magnetic disk device according to claim 2, wherein when there is an error in the data comparison result, firstly, the test data signal is rewritten in the CSS zone. Secondly, the test data signal of the rewritten CSS zone is read again, and the magnetic disk medium (1a) may cause data corruption depending on whether or not the second test data read signal has the error. A test method for the degree of data destruction difficulty in a magnetic disk device, which is characterized by testing whether or not it is likely to occur. 5. The test method for data destruction difficulty in a magnetic disk device according to claim 3, wherein if there is a difference in the comparison results of the signal amplitudes, then firstly, the test data signal is sent to the CSS zone. Re-writing, secondly, re-reading the re-written CSS zone test data signal, and determining whether or not the second test data read-out signal has the signal amplitude difference, the magnetic disk medium (1a The test method for the degree of data destruction difficulty in a magnetic disk device is characterized in that: