System and method of defect description of a data storage medium

The disclosure is directed toward systems and methods of defect description of a data storage medium. In a particular embodiment, a method includes determining a first defect of a data storage medium. The method also includes determining a format of an entry of a defect description table based on the first defect and a location of a second defect of the data storage medium. The format is selected from one of a plurality of formats. The method also includes storing a description of the first defect in the entry of the defect description table in the format.

BACKGROUND

The present disclosure is generally related to defect description of a data storage medium. During a manufacturing certification process of a data storage medium, defective sectors can be identified and recorded in a defect description table (DDT). If a storage size allocated for a defect description table does not have sufficient capacity to record all of the defective sectors, the data storage medium may be rejected during the manufacturing certification process.

As data storage medium capacities increase with the introduction of new storage technology, the total number of defective sectors that need to be identified in the DDT increases. For example, a physically damaged media area of the data storage medium may yield more defective sectors with increased capacity for tracks per inch (TPI) or bytes per inch (BPI) on the media. All defective sectors typically need to be recorded in the defect description table, but the space requirements for recording all of the defective sectors in increasingly large data storage mediums may be more of a problem as capacities increase.

One solution to the increasing capacity requirements of defect description tables may be to increase the storage size allocated for the defect description table. However, defect description tables and user cache may both make use of buffer memory of a data storage device and unless the buffer memory is increased in size, a larger defect description table may reduce the amount of the user cache that that is available for the buffer memory. Additionally, increasing the size of the buffer memory may increase the cost of the data storage device. Cache performance may also suffer if the size of the defect description table is increased. Therefore, there is a need for an improved system and method of defect description of a data storage medium.

SUMMARY

In a particular embodiment, a method includes determining a first defect of a data storage medium and determining a format of an entry of a defect description table based on the first defect and a location of a second defect of the data storage medium. The format is selected from one of a plurality of formats. The method further includes storing a description of the first defect in the entry of the defect description table in the format.

DETAILED DESCRIPTION

The disclosure is directed toward systems and methods of defect description of a data storage medium. In a particular embodiment, a method includes determining a first defect of a data storage medium. The method also includes determining a format of an entry of a defect description table based on the first defect and a location of a second defect of the data storage medium. The format is selected from one of a plurality of formats. The method also includes storing a description of the first defect in the entry of the defect description table in the format.

In another embodiment, a method is disclosed that includes accessing a defect description table of a data storage medium. The defect description table includes defect description data in a plurality of distinct formats. Each entry of the defect description table has one of the plurality of distinct formats. Each of the plurality of distinct formats is based on a relationship between a location of a first defective portion of the data storage medium and a location of a second defective portion of the data storage medium. The method also includes determining when a portion of the data storage medium is defective based on the defect description table.

In another embodiment, a device is disclosed that includes a transducer operable to read data from a data storage medium. The device also includes a controller adapted to receive the data via the transducer and determine when a portion of the data storage medium is defective based on defect description data. The defect description data includes at least one entry in a table and the at least one entry has one of a plurality of formats. At least one of the plurality of formats describes a relationship of a first defective portion of the data storage medium to a second defective portion of the data storage medium. The controller is adapted to process each of the plurality of formats.

In yet another embodiment, a computer readable medium having instructions to cause a processor to execute a method including accessing a defect description table of a data storage medium. The defect description table includes defect description data in a plurality of distinct formats. Each entry of the defect description table has one of the plurality of distinct formats. Each of the plurality of distinct formats is based on a relationship between a location of a first defective portion of the data storage medium and a location of a second defective portion of the data storage medium. The method also includes determining when a portion of the data storage medium is defective based on the defect description table.

Referring toFIG. 1, in a particular embodiment, a disc drive100includes a base102to which various components of the disc drive100are mounted. A top cover104, shown partially cut away, cooperates with the base102to form an internal, sealed environment for the disc drive. The components of the disc drive100include a spindle motor106, which rotates one or more discs108. Information is written to and read from tracks on the discs108through the use of an actuator assembly110that rotate about a bearing shaft assembly112positioned adjacent the discs108. The actuator assembly110includes one or more actuator arms114that extend toward the discs108, with one or more flexures116extending from the actuator arms114. Mounted at the distal end of each of the flexures116is a head118including an air bearing slider (not shown) that enables the head118to fly in close proximity above the corresponding surface of the associated disc108.

The track position of the heads118is controlled, during a seek operation, through the use of a voice coil motor (VCM)124that typically includes a coil126attached to the actuator assembly110, as well as one or more permanent magnets128that establish a magnetic field in which the coil126is immersed. The controlled application of current to the coil126causes magnetic interaction between the permanent magnets128and the coil126so that the coil126moves in accordance with the well-known Lorentz relationship. As the coil126moves, the actuator assembly110pivots about the bearing shaft assembly112, and the heads118are caused to move across the surfaces of the discs108.

A flex assembly130provides requisite electrical connection paths for the actuator assembly110while allowing pivotal movement of the actuator assembly110during operation. The flex assembly130can include a printed circuit board132to which head wires (not shown) are connected. The head wires may be routed along the actuator arms114and the flexures116to the heads118. The printed circuit board132may include circuitry for controlling the write currents applied to the heads118during a write operation and a preamplifier (not shown) for amplifying read signals generated by the heads118during a read operation. The flex assembly130terminates at a flex bracket134for communication through the base102to a disc drive printed circuit board (not shown) mounted to the disc drive100.

As shown inFIG. 1, a plurality of nominally circular, concentric tracks109are located on the surface of the discs108. Each track109includes a number of servo fields that are interspersed with user data fields along the track109. The user data fields are used to store user data, and the servo fields are used to store servo information used by a disc drive servo system to control the position of the heads118.

FIG. 2provides a functional block diagram of the disc drive100. A hardware/firmware based interface circuit200communicates with a host device (such as a personal computer, not shown) and directs overall disc drive operation. The interface circuit200includes a programmable controller220with associated microprocessor224and memory230. In a particular embodiment, memory230is a first-in-first-out (FIFO) buffer. The interface circuit200also includes a buffer202, an error correction code (ECC) block204, a sequencer206, and an input/output (I/O) control block210.

The buffer202temporarily stores user data during read and write operations, and includes a command queue (CQ)208where multiple pending access operations are temporarily stored pending execution. The buffer202may be a volatile or non-volatile solid state memory device. The ECC block204applies on-the-fly error detection and correction to retrieved data. The sequencer206asserts read and write gates to direct the reading and writing of data. The I/O block210serves as an interface with the host device.

FIG. 2further shows the disc drive100to include a read/write (R/W) channel212which encodes data during write operations and reconstructs user data retrieved from the discs108during read operations. A preamplifier/driver circuit (preamp)132applies write currents to the heads118and provides pre-amplification of readback signals.

A servo control circuit228uses servo data to provide the appropriate current to the coil216to position the heads118. The controller220communicates with a processor1226to move the heads118to the desired locations on the discs108during execution of the various pending commands in the command queue208.

During operation, the controller220may determine a first defective portion of the disc108. The controller220may determine a format of an entry of a defect description table based on the first defective portion and a location of other defects on the disc108. The format may be selected from one of a plurality of formats. The controller220may also store a description of the first defect in the entry of the defect description table in the format. The format may be based on which of the plurality of formats will result in a least number of entries in the defect description table.

In a particular embodiment, the defect description table may store defect location information in multiple defect description sub-tables. The defect description sub-tables may have unique formats for storing data to identify a defective location of the disc108. The controller220may select a format for an entry in the defect description table that corresponds to one of the defect description sub-tables.

Referring toFIG. 3, an embodiment of a system of defect description of a data storage medium is depicted and generally designated300. The system300includes a defect description table302that may be located in a dedicated system area of a data storage medium304of the system300. The dedicated system area may be an area that may have a higher reliability than another area of the data storage medium304. In another embodiment, the defect description table302may be stored in a solid state memory of a data storage device, such as the buffer202shown inFIG. 2. The solid state memory may be volatile or non-volatile.

In a particular embodiment, the data storage medium304may be a rotatable data storage medium including a plurality of tracks that each have a plurality of sectors to store data in. For example, the data storage medium304may be a magnetic data storage medium, such as one of the discs108of the disc drive100shown inFIG. 1. In another example, the data storage medium304may be an optical data storage medium, a magneto-optical data storage medium, or any other type of data storage medium that may need to have defect locations stored.

Referring toFIG. 4, a block diagram representation of a data storage medium having defects is depicted and generally designated400. In a particular embodiment, the data storage medium400may be a rotatable data storage medium including a plurality of tracks that each have a plurality of sectors to store data in. For example, the data storage medium400may be a magnetic data storage medium, such as the discs108of the disc drive100shown inFIG. 1. The data storage medium400may also be an optical data storage medium, a magneto-optical data storage medium, or any other type of data storage medium that may need to have defect locations stored. For example, the data storage medium400may be the data storage medium304shown inFIG. 3.

As shown, the data storage medium400includes a first track402designated “Track N”. The first track402includes sectors404-428. In the first track402, sector406may be defective and may be designated as defect “A”. In the first track402, sectors410,412,414and416may be defective and that group of sectors may be designated as defect “B”. Apparatus400also includes a second track434designated “Track N+1”. The second track434includes sectors436-460. In the second track434, sectors442,444,446and448may be defective and that group of sectors may be designated as defect “C”. Further, Apparatus400includes a third track464designated “Track N+2”. The third track464includes sectors466-490. In the third track464, sector468may be defective and may be designated as defect “D”. Also, in the third track464, sectors480and482may be defective and that group of sectors may be designated as defect “E”. Further, in the third track464, sector488may be defective and may be designated as defect “F”.

Referring toFIG. 5, a block diagram of an embodiment of a data structure of a defect description of a data storage medium is depicted and generally designated500. The data structure500may be represented as a defect description table. The defect description table may include a first defect description sub-table504, a second defect description sub-table506, and a third defect description sib-table502. The defect description sub-tables502,504, and506may have unique formats for storing data to identify a defect location of a data storage medium. A device that creates or modifies the defect description table may select a format that corresponds to one of the defect description sub-tables502,504, and506to store defect location information. The defect descriptions shown in the defect description sub-tables502,504, and506are based on the defects shown in the data storage medium400inFIG. 4.

The first defect description sub-table504may store defect information related to a defect that may span multiple adjacent tracks. The first defect description sub-table504may have multiple entries. The first defect description sub-table504may store, in a single entry, defect information that corresponds to several defective sectors in adjacent tracks that start from the same physical sector within their respective track and have identical or substantially similar sector span.

In a particular embodiment, the first defect description sub-table504may include an entry index field520. The entry index field520may contain a unique identifier that provides each entry in the first defect description sub-table504with a unique identification. An example of an entry index for a first entry in the first defect description sub-table504may be zero “0” as shown inFIG. 5.

The first defect description sub-table504may also include a defect starting track field522that indicates a starting track of a series of multiple adjacent tracks that contain a defective sector. An example for defect “B” shown inFIG. 4may have the defect starting track entry designated as “N” for the first track402. Alternatively, the second track434inFIG. 4may be chosen as the starting track.

The first defect description sub-table504may also include a sector/sector span field524that describes a starting position at which a defect starts in the track identified in the defect track field522. The starting position may be described as a number of sectors offset from a point of the identified track, such as a start of a track. The sector/sector span field524also describes a number of consecutive sectors of the defect. The number of sectors may be one or more. An example of a sector/sector span entry that represents defect “B” and defect “C” shown inFIG. 4may be “3/4” because both defects are offset into each track by three sectors and are four sectors in length.

The first defect description sub-table504may also include a track span width field526that describes a number of adjacent tracks that may be included in the entry for the defect description. The number of adjacent tracks may be based off of adjacent tracks that have an identical or substantially similar defect pattern. An example of a track span width entry may be “2” for defects “B” and “C” shown inFIG. 4representing the number of adjacent tracks with an identical or substantially similar defect pattern.

The second defect description sub-table506may store, in a single entry, defect information related to multiple defects in a single track. The second defect description sub-table506may have multiple entries. In a particular embodiment, the second defect description sub-table506may be one sub-table with a specific number of defects per track. In another particular embodiment, the second defect description sub-table506may be may be multiple sub-tables each having a different number of defects per track. In the second defect description sub-table506, a single entry may represent a plurality of defects on a single track.

In a particular embodiment, the second defect description sub-table506may include an entry index field530. The entry index field530may contain a unique identifier that provides each entry in the second defect description sub-table506with a unique identification. An example of an entry index for a first entry in the third defect description sub-table506may be zero “0” as shown inFIG. 5.

The second defect description sub-table506may also include a defect track defect track field532that indicates a track that contains one or more defective sectors. An example of a defect track entry for defects “D”, “E”, and “F” shown inFIG. 4shows the defect track designated as “N+2” for the third track464.

The second defect description sib-table506may also include one or more sector/sector span fields534,536, and538, each of which describes a starting position of a defect pattern and describes a number of defective consecutive defective sectors in each defect pattern. For example, a sector/sector span entry that represents the plurality of defects “D”, “E”, and “F” in the third track464shown inFIG. 7may be “1/1” for defect “D”, representing an offset of 1 and being 1 sector in length, “7/2” for defect “E”, representing an offset of 7 and being 2 sectors in length, and “11/1” for defect “F”, representing an offset of 11 and being 1 sector in length.

The third defect description sub-table502may store defect information related to a single defect in a single track. The third defect description sub-table502may have multiple entries related to single defects in different tracks.

In a particular embodiment, the third defect description sub-table502may include an entry index field510. The entry index field510may contain a unique identifier that provides each entry in the third defect description sub-table502with a unique identification. An example of an entry index for a first entry in the first defect description sub-table502may be zero “0” as shown inFIG. 5.

The third defect description sub-table502may also include a defect track field512that indicates a track that contains a defective sector. An example for defect “A” shown inFIG. 4shows the defect track entry designated as “N” for the first track402.

The third defect description sub-table502may also include a single sector/sector span field514that describes a starting position at which a single defect starts in the track identified in the defect track field512. The starting position may be described as a number of sectors offset from a point of the identified track, such as a start of a track. The sector/sector span field514also describes a number of consecutive sectors of the defect. The number of sectors may be one or more. An example of a sector/sector span entry that represents the defect “A” shown inFIG. 4may be “1/1”, representing an offset of 1 and being 1 sector in length.

In other embodiments, there may be more or less defect description sub-tables. For example, a defect description sub-table, similar to the third defect description sub-table506, may contain a different number of sector/sector span fields, such as two sector/sector span fields or four sector/sector span fields.

In another particular embodiment, some defect descriptions may be able to use more than one format, e.g. sub-table. When this occurs, a format that achieves a greatest condensing effect compared to the other available formats may be used.

Referring toFIG. 6, a flow diagram of an embodiment of defect description of a data storage medium is depicted and generally designated600. The method600may include determining a first defect of a data storage medium, at602. The first defect may be detected by a data storage device or by another device during a manufacturing process of the data storage medium. The first defect may also be detected during operation of the data storage medium.

The method600may also include determining a format of an entry of a defect description table based on the first defect and a location of a second defect of the data storage medium. The format may be selected from one of a plurality of formats. The method600may also include storing a description of the first defect in the entry of the defect description table in the format. The format may be based on which of the plurality of formats will result in a least number of entries in the defect description table.

In a particular embodiment, the method600may include determining a second defect of the data storage medium, at604. The method600may also include determining if the second defect has a substantially similar position within an adjacent track, at606. When the second defect has a substantially similar position as the first defect within an adjacent track, the method600may store the description of the first defect in a first format, at608. The first format may be selected for similar defects in a adjacent tracks. In a particular embodiment, a substantially similar position includes an identical starting location and an identical sector span.

In a particular embodiment, the first format may include a field for storing data that represents a unique identifier for each entry in the first format. The first format may also include a field for storing data that represents a track identification. The first format may further include a field for storing data that represents a starting position of one or more defective sectors on a first track and a number of consecutive sectors after the starting position that are defective on the first track. The first format may also include a field for storing data that represents a number of adjacent tracks having an identical one or more defective sectors.

When the second defect does not have a substantially similar position within an adjacent track, the method600may include determining if the second defect is in the same track as the first defect, at610. When the second defect is in the same track as the first defect, the method600may store the description of the first defect in a second format, at612. The second format may be selected for multiple defects in a single track.

In a particular embodiment, the second format may include a field for storing data that represents a unique identifier for each entry in the second format and a field for storing data that represents a track identification. The second format may also include multiple fields for storing data that represents a starting position of a defect on a track and a number of consecutive sectors after the starting position that are defective on the track.

When the first defect is not in the same track as the second defect, the method600may include storing the description of the first defect in a third format, at614. The third format may be distinct from the first format and the second format. In a particular embodiment, the third format is a format selected for a single defect in a single track.

In a particular embodiment, the third format may include a field for storing data that represents a unique identifier for each entry in the third format and a field for storing data that represents a track identification. The third format may also include a field for storing data that represents a single defective sector.

Referring toFIG. 7, a flow diagram of a third embodiment of a method of defect description of a data storage medium is depicted and generally designated700. The method700includes accessing a defect description table of a data storage medium, at702. The defect description table may include defect description data in a plurality of distinct formats. Each entry of the defect description table may have one of the plurality of distinct formats. Each of the plurality of distinct formats may be based on a relationship between a location of a first defective portion of the data storage medium and a location of a second defective portion of the data storage medium.

The method700may also include determining when a portion of the data storage medium is defective based on the defect description table, at704. In a particular embodiment, the data storage medium includes data tracks. The plurality of distinct formats may include a first format for a single entry that describes defective portions that have the same position within each of a plurality of adjacent tracks and a second format for a single entry that describes a plurality of defective portions in a single track.

In a particular embodiment, the first format may include a field for storing data that represents a unique identifier for each entry, a field for storing data that represents a track identification, a field for storing data that represents a starting position of one or more defective sectors on a first track and a number of consecutive sectors after the starting position that are defective on the first track, and a field for storing data that represents a number of adjacent tracks having an identical one or more defective sectors.

In another particular embodiment, the second format may include a field for storing data that represents a unique identifier for each entry, a field for storing data that represents a track identification, and multiple fields for storing data that each represent a starting position of one or more defective sectors on a second track and a number of consecutive sectors after the starting position that are defective on the second track.

In a particular embodiment, the identification of a portion of the data storage medium in the defect description table may be an indication that the portion is defective, in which case, an indication that the portion of the data storage medium may be defective may be transmitted, at706. When the portion may be not identified in the defect description table, an indication that the portion may be not defective may be transmitted, at708.

In accordance with various embodiments, the methods described herein may be implemented as one or more software programs running on a computer processor or controller, such as the controller220. In accordance with another embodiment, the methods described herein may be implemented as one or more software programs running on a host device, such as a PC that is using a disc drive. Dedicated hardware implementations including, but not limited to, application specific integrated circuits, programmable logic arrays and other hardware devices can likewise be constructed to implement the methods described herein.