Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
2000-03-31
2004-03-02
Baderman, Scott (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S005110
Reexamination Certificate
active
06701465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a defect information management method and apparatus, and more particularly to a method and apparatus for management of defect information used to locate defects of a storage medium in a magnetic disk system.
2. Description of the Related Art
FIG. 1
schematically shows a magnetic disk system in which defect information, used to locate defects of a storage medium, is handled.
A typical example of the magnetic disk system is a hard disk drive that includes a number of platters as the storage medium, each platter requiring two read/write heads, one for each side.
As shown in
FIG. 1
, the magnetic disk system
1
generally comprises a magnetic disk
2
, a spindle motor
3
, a read/write head
4
, a head arm
5
, a voice coil motor (VCM)
6
, a rotating shaft
7
, a spindle shaft
8
, a motor controller/driver (MC/D)
9
, a micro control unit (MCU)
10
, a flash read-only memory (flash ROM)
11
, a hard disk controller (HDC)
12
, an interface circuit (I/F)
13
, a data buffer
14
, and a read/write channel
15
.
In the magnetic disk system
1
of
FIG. 1
, the magnetic disk
2
is a storage medium for recording information. The magnetic disk
2
is accessed by the read/write head
4
so as to read information from or write information to the magnetic disk
2
. The disk
2
is fixed to the spindle
8
of the spindle motor
3
, and the spindle motor
3
rotates the disk
2
around the spindle
8
.
The MCU
10
controls the spindle motor
3
by using the motor controller/driver (MC/D)
9
. The MCU
10
controls the read/write channel
15
so as to supply a reading/recording signal to the read/write head
4
. The read/write head
4
is positioned over the disk surface of the magnetic disk
2
rotated by the spindle motor
3
. In accordance with the received reading/recording signal, the read/write head
4
produces magnetic fields to read and record bit streams on the appropriate track of the disk
2
.
The read/write head
4
is connected to the head arm
5
, and the head arm
5
is associated with the VCM
6
. The VCM
6
is an actuating mechanism that positions the read/write head
4
over the appropriate track of the disk
2
. The MCU
10
controls the VCM
6
by using the MC/D
9
. Under the control by the MCU
10
, the VCM
6
moves the read/write head
4
in a radial direction of the disk
2
, so as to allow the read/write head
4
to trace the appropriate track of the disk
2
.
A host system (not shown in
FIG. 1
) sends a control signal to the HDC
12
via the I/F
13
. The HDC
12
receives the control signal and delivers it to the MCU
10
, and the MCU
10
controls the entire disk system in response to the received control signal. The flash ROM
11
stores information that was processed by the MCU
10
.
The data buffer
14
is made up of a dynamic random access memory (DRAM). The data buffer
14
temporarily stores information that was processed by the MCU
10
. Further, the data buffer
14
provides a storage area in which the defect information, used to locate defects of the storage medium
2
, is laid out.
FIG.
2
A and
FIG. 2B
show a data structure on the storage medium of the magnetic disk system of FIG.
1
.
In the magnetic disk system of
FIG. 1
, the read/write head
4
is moved along the disk surface of the disk
2
which is rotated by the motor
3
. A circular path that the disk
2
traces out under the head
4
is called a track. The magnetic disk
2
is usually a metal disk covered with a magnetic material for recording information. As shown in
FIG. 2A
, the disk
2
contains a number of tracks “Tr
1
” through “Trn” on the disk surface. Each track is identified by a track number. A sector is a unit of a track that is physically read or written at the same time. In the example of
FIG. 2A
, tracks are divided into a number of sectors “S
1
” through “Sm”. Each sector is identified by a sector number.
In the case where the magnetic disk
2
is in the form of a number of platters (for example, a hard disk drive), a cylinder that is a stack of tracks at one actuator position is defined. Typically, in such a magnetic disk system, the storage medium is divided into a number of cylinders, and each cylinder is identified by a cylinder number.
FIG. 2B
shows a format of data in each of the number of sectors “S
1
” through “Sm” of the magnetic disk
2
for the example of FIG.
2
A. As shown in
FIG. 2B
, each sector is made up of a servo information field “SB” and a data field “D”. The data field D contains information bits recorded in the disk
2
. The servo information field SB contains servo information used to position the read/write head
4
over a desired track of the magnetic disk
2
.
In order to identify respective defects of the magnetic disk
2
, a conventional defect list is produced. Once a defect at any location of the disk
2
is detected, defect information, indicative of the location of the defect on the disk
2
, is inserted into the conventional defect list. When producing the conventional defect list, a layout table that indicates arrangement of normal sectors and defective sectors on the disk
2
is often used.
FIG. 3
shows a conventional layout table which is used to indicate arrangement of normal sectors and defective sectors on a storage medium.
In the layout table of
FIG. 3
, a head number is provided to specify one of the rows of the table, and it indicates a particular position on the storage medium where the read/write head is located for a corresponding one of the platters of the storage medium. In the present example, the head number ranges from
0
to
3
, and there are four rows in this table. In the layout table of
FIG. 3
, a sector number is provided to specify one of the columns of the table, and it indicates a particular position on the same track of the storage medium. In the present example, the sector number ranges from
0
to
6
, and there are seven columns in this table.
One of the records in columns and rows of the conventional layout table of
FIG. 3
is normally described by an identifier, which is hereinafter called a logical sector identifier.
As shown in
FIG. 3
, the logical sector identifier in the row of head
0
changes from
0
to
6
. No defect item is contained in the row of head
0
. The logical sector identifier in the row of head
1
starts from
7
.
When a defect item is included as one of the records in the layout table of
FIG. 3
, the defect item is described by a different identifier, which is hereinafter called a defect identifier. In the present example, two kinds of defect which may take place on the storage medium are considered: slip defects and alternative defects.
If a slip defect exists in a certain sector of the storage medium, the access to the defective sector of the storage medium jumps from a preceding sector before the defective sector to a following sector after the defective sector. The defect identifier for slip defects consists of the character “S” and a sequential number. In the layout table of
FIG. 3
, the records at the locations (head
1
, sector
1
) and (head
2
, sector
5
) are indicated by “S
1
” and “S
3
”, which shows that the slip defects (the first and third defects) exist at these locations of the storage medium. The defect item “S
1
” is contained in the row of head
1
, and the logical sector identifier in the row of head
1
changes from
7
to
12
by taking no account of the sector “S
1
” with the slip defect.
If an alternative defect exists in a certain sector of the storage medium, the access to the defective sector of the storage medium jumps to another secondary sector of the storage medium. The defect identifier for alternative defects consists of the character “R” and a sequential number. The identifier for a secondary sector for an alternative defect becomes the logical sector identifier for the location of the alternative defect.
In
FIG. 3
, “SP” indicates a spare sector in the storage medium. In the layout table of
FIG. 3
, the record at the location (head
2
, sector
Greer Burns & Crain Ltd.
McCarthy Christopher S.
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