Abstract:
A method and system for laying out and accessing data in a disk drive system. The layout resides in a table in firmware of the disk drive system. The table includes multiple entries or rows, one corresponding to each different area in the disk media. The entry provides information about the range of block addresses in that area including the starting and end block address in the area, and information about the range of physical addresses including the head and the starting and ending cylinder number. A firmware routine finds the appropriate entry in the table and converts the block address to the physical address, or vice versa.

Description:
[0001]    This application claims priority from U.S. Provisional Patent Application No. 60/076,323, filed on Feb. 27, 1998, the contents of which are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the field of disk drives, and in particular, to a system for ordering or laying-out data blocks on a disk drive.  
         BACKGROUND OF THE INVENTION  
         [0003]    Most personal computers include at least one disk drive system for storage of data. Typically, disk drive systems include one or more (e.g., three) disks or platters, generically referred to as the recording media. The platters are each connected in a spaced-apart fashion to a spindle that is employed to rotate or spin the platters. Typically, one read/write head is provided for each side or surface of each platter. The heads are mounted on actuators that can be moved radially relative to the platters.  
           [0004]    Another major component of disk drive systems is the firmware that controls the disk drive. Disk drive firmware is the software that is embedded in the disk drive system and executes on a local disk controller processor(s), to direct overall drive operation. Typically, disk drive firmware is used to control at least: (1) the spinning of the disk drive spindle; (2) the movement of the actuator arms; and (3) the data path between the read/write heads and the host computer. The design of the firmware in a disk drive system is one of the major expenses in the design of the entire system.  
           [0005]    One of the responsibilities of the firmware is to order the data on the media, which means to arrange the data on the media in an optimum way based on potentially many different factors. Some of the factors that may influence the optimum ordering of the data include, but are not limited to: (1) the amount of time it takes to perform a head switch operation (the operation of transitioning between reading or writing with one head to reading or writing with a different head); (2) the amount of time it takes to perform a cylinder switch operation (the operation of moving the actuator to position the read/write head at a different radial position relative to the media); (3) the sequential transfer rate desired from disk transfers; and (4) maximizing the readability of certain types of data  
           [0006]    For the purpose of data storage, the disk media is addressed using vectors that include, but are not limited to, the following: (1) cylinder, which corresponds to the radius on the media at which the data is located; (2) head, which corresponds to a particular side or surfaces of a particular platter on which the data is located; and (3) sector, which corresponds to the rotational position of the media at which the data is located.  
           [0007]    This addressing is commonly referred to as the “physical” address of the data. The term “track” is used as a reference to the combination of a cylinder and head address. In other words, a particular cylinder can be found on each surface, but a track can only be found on one surface. For example, a disk drive with 1000 cylinders and 4 heads has 4000 tracks. The term “block” is used to describe the addressable resolution of the disk drive as presented to the host. A sector is the physical rotational position on a track where blocks of data can be stored (e.g., 500 sectors per track for a particular radial zone of the media). Most modern disk drives use 512 byte blocks and 512 byte sectors, so the terms are used interchangeably. However, some disk drives use a different block size and/or have a block size that does not match the sector size. A “block address” is thus a number representing the address of a block to the host computer. Sequential transfers to or from the host computer always go in the order of the block address.  
           [0008]    When choosing to order sequential blocks on the media, the firmware designer can implement any one of the following methods:  
           [0009]    (1) Surface mode, where sequential blocks on the disk drive include all sectors on the outermost track of a given surface, followed by all sectors on the next track at lesser radius of the same surface, and so on to the innermost track of the surface, followed by the outermost track of the next surface, and so on. This method minimizes head switch operations on sequential transfers because the majority of track switches do not involve a head switch, but it does require an actuator movement together with each head switch.  
           [0010]    (2) Cylinder mode, where sequential blocks on the disk drive include all sectors of the outermost track of a given surface, followed by all sectors on the outermost track of the next surface, continuing through all outermost tracks of all surfaces, then proceeding to the next track at lesser radius of the original surface, and repeating the process through all of the tracks on the innermost cylinder. This method causes a higher percentage of track switches on sequential transfers to involve a head switch operation.  
           [0011]    (3) Serpentined surface mode, which starts like surface mode, but then after transferring all sectors on the innermost track of the first surface, the ordering proceeds to the innermost track of the next surface and then proceeds in an outward direction. This method minimizes head switch operations, as with surface mode. In addition, it avoids the large actuator movement when proceeding from one surface to another.  
           [0012]    (4) Serpentined cylinder mode, which starts like cylinder mode, but then after transferring all sectors on the outermost track of the last surface, the ordering proceeds to the next innermost cylinder but remains on the same surface. This method makes sure that a head switch and an actuator movement never occur on the same sequential track switch.  
           [0013]    It is often advantageous to use combinations of the above modes, or to use modes different than those described. For example, the designer may choose to put some maintenance type information such as a defective sector list on the outer tracks of a drive in cylinder mode to make sure that copies are stored on multiple heads. Processing could then proceed with the user data in surface mode to match the block ordering with the performance characteristics of the servo system.  
           [0014]    Furthermore, it is not unusual to have the starting or ending points at places other than the outermost or innermost circumference of the media. For example, the designer may choose to place the lowest numbered blocks near the center of the media, to maximize performance based on the operating characteristics of a given operating system. Or he may choose to have the first n blocks scattered around the media because they contain the defect list copies and it is important to minimize the possibility of the loss of the defect list due to debris on the media.  
           [0015]    Therefore, although surface mode, cylinder mode, and serpentined versions of the same are general approaches that are commonly used, there are many cases in which it may be advantageous to place the data and order the sequential transfers in other ways, variations of these standard ways, and/or combinations of the above.  
           [0016]    In most, if not all, prior art disk drive systems, the mode is hard-coded in firmware to create the layout or path followed through the media in the placement of sequential data. With the design of such systems, the firmware must be re-written from scratch if it is desired to create a different layout. This can add significantly to the design cost of such systems.  
           [0017]    Since firmware development is a major cost component of the overall development of a disk drive, it is advantageous to re-use, or ‘leverage’ the firmware development effort on a particular disk drive product or model into other disk drive products or models. Often, the different operating characteristics, environmental conditions, and/or intended applications of different disk drive models causes the optimum block placement and ordering on the media to vary between the models. In existing systems, this can result in a great deal of additional firmware development effort to provide a calculation that is optimized for each disk drive model.  
           [0018]    There exists a need for a method in which the relationship of block address to physical address of data on the media can be easily configured, thus allowing maximum reuse of firmware between disk drive models and reducing development time and cost. It is against this background, and the desire to solve the problems of and improve on the prior art, that the present invention has been developed.  
         SUMMARY OF THE INVENTION  
         [0019]    The present invention relates to a method of accessing data on disk media in a disk drive system. The system has control circuitry with associated memory. The method includes providing a data layout table containing the layout of the data in a tabular form in the associated memory of the control circuitry. Upon external requests to access data in the disk drive system, the external request including a block address, the method includes converting the block address in the external request to a physical address by accessing the data layout table. The method also includes accessing the data on the disk media by utilizing the physical address.  
           [0020]    The converting operation may include locating an entry in the data layout table and calculating a head number from the entry in the data layout table and the block address. The converting operation may also includes calculating a cylinder number from the entry in the data layout table and the block address and calculating a sector number from the entry in the data layout table and the block address. The calculating a cylinder number operation may include calculating a cylinder offset from the entry in the data layout table and the block address and calculating the cylinder number from the cylinder offset and a starting cylinder for the entry in the data layout table. The calculating a cylinder number may further include determining if a direction in the entry in the data layout table is forward or backward.  
           [0021]    The present invention is also directed to a disk drive system for storing data. The system includes at least one storage disk, the disk having a storage surface thereon on which data can be stored. The system also includes at least one sensor operatively associated with the storage surface, the sensor generating signals representative of the data stored on the storage surface. Further, the system includes control circuitry associated with the storage disk and the sensor, the control circuitry including circuitry for determining where on the storage disk a particular segment of data is stored. The determining circuitry includes a table providing a layout of the data on the storage disk, the table being employed to determine where the particular segment of data is stored.  
           [0022]    The table may include entries for corresponding areas of the storage surface. The table may include block addresses and physical addresses. The physical addresses may include head, cylinder, and sector information. The determining circuitry may convert between the block addresses and the physical addresses. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 is a simplified block diagram of a disk drive system of the present invention.  
         [0024]    [0024]FIG. 2 is a table containing layout information representative of the table implemented in firmware in the disk drive system of FIG. 1.  
         [0025]    [0025]FIG. 3 is an pictorial example of the layout described in the table of FIG. 2.  
         [0026]    [0026]FIG. 4 is a flowchart of the process flow followed by firmware within control circuitry of the disk drive system of FIG. 1 in converting a block address to a physical address.  
         [0027]    [0027]FIG. 5 is a flowchart of the process flow followed by firmware within control circuitry of the disk drive system of FIG. 1 in converting a physical address to a block address. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    The present invention includes a block ordering system implemented in a disk drive system  10 , shown in FIG. 1. The disk drive system  10  includes a plurality of platters  12  attached to a spindle  14 . Each platter  12  has an upper surface  16  and a lower surface  18 . Corresponding to each surface  16  and  18  is one of a plurality of read/write heads  20  supported by an arm  22  of an actuator  24 . The platters  12  are spun via the spindle  14  by a motor  26 . Control circuitry  28  controls the motor  26 , the actuator  24 , and the transfer of data to and from the read/write heads  20 . The control circuitry  28  includes a microprocessor  30  having firmware associated therewith and stored in memory device  32 .  
         [0029]    Stored within the firmware associated with the microprocessor  30  is a table  40  (FIG. 2) that describes a layout  42  (FIG. 3) of data blocks on the media (platters). The layout  42  includes the path to be traversed by the read/write heads  20  in accessing sequential blocks of data for a host computer (not shown). This table  40  provides a mapping between logical block addresses and physical block addresses. In other words, the table  40  provides a definition of the mode to be employed in accessing data—be it surface mode, cylinder mode, a serpentined version of one of these modes, any combination of these modes, or some other mode.  
         [0030]    The table  40  maps block ranges to track ranges. Each row in the table  40  contains a block range and the track ranges that the block ranges map to. The table  40  contains an entry for every head switch, and could contain more entries up to one or more for every track. In addition to this mapping between the two types of addresses, each row will also contain the direction in which the entry will progress. The term “direction” describes how the head  20  progresses along the disk surface between the inner and outer diameter. When the direction is forward, then the head is traversing from outer diameter, or lower cylinder number, to the inner diameter, or higher cylinder number. When the direction is backwards, then the head is traversing from inner diameter to the outer diameter. The firmware  40  can access and use the table  40  to traverse the disk.  
         [0031]    For example, suppose the simplified layout  42  shown in FIG. 3 is to be employed for the disk drive system  10 . The layout  42  begins at the outer diameter (OD), or Minimum Cylinder, of Head 1  and proceeds forward on Head 1  to a point equidistant between the OD and the inner diameter (ID), called the Halfway Cylinder. The area described will be referred to as Area 1 . A head switch is next performed while staying on the same cylinder so that the layout continues now on Head 0  while proceeding forward from the Halfway Cylinder to the ID, or Maximum Cylinder. This second area described will be referred to as Area 2 . A head switch is next performed while staying on the same cylinder so that the layout continues now on Head 1  while proceeding backward from the Maximum Cylinder to the Halfway Cylinder. This third area described will be referred to as Area 3 . A head switch is next performed while staying on the same cylinder so that the layout continues now on Head 0  while proceeding backward from the Halfway Cylinder to the Minimum Cylinder. This fourth area described will be referred to as Area 4 . As can be appreciated, the layout  42  follows a figure-8 pattern. Of course, many other patterns could be followed, this being only a simplified example to illustrate the invention.  
         [0032]    The table  40  provides all of the information needed for the firmware to instruct the system  10  to follow this layout  42 . As can be appreciated, the table  40  includes four rows, one for each of the areas (Area 1 , Area 2 , Area 3 , and Area 4 ) in the layout  42  described above. Of course, other layouts may require many more rows in the table such as thirty or more, for example. The table  40  has columns for: (1) the first, or starting, logical block in the area; (2) the last, or ending, logical block in the area; (3) the first, or starting, cylinder in the area; (4) the last, or ending, cylinder in the area; and (5) the head corresponding to the area. Of course, the data could be provided in another format, or more columns could be provided to provide each of the starting and ending blocks in two words or segments of data such as a most significant word and a least significant word, for example.  
         [0033]    The firmware in the disk drive system  10  can use the table  40  to correlate a block address to a cylinder/head/sector address. This can be done when it is desired to convert a block address to a physical address, or when it is desired to convert a physical address to a block address. The conversion of block address to a physical address is shown in the flow chart  100  of FIG. 4. A software or firmware routine can be written to follow this flow chart  100  to be used in interpreting or accessing the table  40 . The flow chart  100  is seen to begin with two inputs that are provided to the process. First of all, the table  40  is provided ( 102 ), and also the block address is provided ( 104 ) for which a corresponding physical address is desired. Next, a step is performed ( 106 ) to find the line in the table  42  that contains the input block address. This is accomplished by searching the block addresses in the table  42  and finding the row where the input address is between the starting and ending block address. In other words, (starting block address)≦(input block address)≦(ending block address). A pointer for that row or line is passed on to the next step in the process.  
         [0034]    Next, a test is performed ( 108 ) to determine if an existing line was found that satisfied the above condition. If not, then the routine outputs ( 110 ) an error message. If the line did exist, the next step is to calculate ( 112 ) the number of blocks into the given area to the input block address. In other words, an offset is calculated that is (block offset)=(input block address)−(starting block address). The block offset is then provided to the next step ( 114 ) where a calculation is made of the number of cylinders into the area. This cylinder offset is calculated from the block by the whole number portion of the quotient from block offset divided by the number of blocks per track. The number of blocks per track is known for each zone of the platters. This information can be stored in a separate table (not shown) or, alternatively, could be provided as an additional column in the table  40 . For example, an outer zone of a platter may have 500 blocks per track, with the next inner-most zone of the platter having 450 blocks per track, and so forth. So (cylinder offset)=(block offset) DIV (blocks per track) provides the cylinder offset. The sector number is provided by the remainder from the calculation of block offset divided by blocks per track. This can be performed by the calculation of (sector number)=(block offset) MOD (blocks per track).  
         [0035]    The head number from the table, the cylinder offset, and the sector number are provided from processing step ( 114 ) to a test ( 116 ) that is performed to determine whether in the area of interest, the direction is forward or backward. The direction is forward for a given row of the table  40  if the ending cylinder number is larger than the starting cylinder number. Thus, in the table  40 , the direction is forward for the rows corresponding to Area 1  and Area 2 , while the direction is backward for the rows corresponding to Area 3  and Area 4 . In the case where the direction is forward, processing flows to step ( 118 ) where the precise cylinder number is calculated from the calculation of (cylinder)=(starting cylinder)+(cylinder offset). If the direction is not forward, then processing flows from test ( 116 ) to step ( 120 ) where the precise cylinder is calculated from (cylinder)=(starting cylinder)−(cylinder offset). After the precise cylinder has been calculated at either step ( 118 ) or step ( 120 ), processing flows to step ( 122 ) where the routine ends with the head number, the cylinder number, and the sector number calculated. In this manner, the block address has been converted to a physical address.  
         [0036]    Occasionally, it is desirable to convert a physical address to the block address, such as during the performance of test procedures, and so forth. The process flow for performing this calculation is shown in a flow chart ( 130 ) in FIG. 5. Since the process of flow chart ( 130 ) is analogous to and the reverse of the process of flow chart  100 , several of the details are very similar. First, two inputs are provided to the flow chart ( 130 ) in the form of the table  40  that is provided ( 132 ) and the desired input physical address ( 134 ) for which a corresponding block address is desired. Step ( 136 ) performs the function of finding the line or row in the table that contains the input physical address. This is done by searching through the cylinder ranges in the table and finding the line where the head number for that row matches the head number in the input physical address and, for forward directions, (starting cylinder)≦(cylinder for the input physical address)≦(ending cylinder), and for backwards directions, (starting cylinder)≧(cylinder for the input physical address)≧(ending cylinder). A pointer to this line or row in the table  40  is provided to the next step.  
         [0037]    Next, a test is performed ( 138 ) to determine if there was an existing line in the table  40  corresponding to the input physical address. If not, an error message is output ( 140 ). If so, the process flows to a test ( 142 ) where it is determined if the direction for the selected row is forward or backwards. This test is performed in a similar fashion to the test ( 116 ) of flow chart  100  (FIG. 4). If the direction is forward, then a cylinder offset is calculated ( 144 ) by the equation (cylinder offset)=(input cylinder)−(starting cylinder). If the direction is not forward, then the cylinder offset is calculated by the calculation ( 146 ) of (cylinder offset)=(starting cylinder)−(input cylinder). In the case of either calculation ( 144 ) or ( 146 ), the cylinder offset is provided to the next processing step. Next, the number of blocks into the area is calculated ( 148 ). This calculation is performed using the cylinder offset and sector number from the input physical address. The block offset calculated is (block offset)=((blocks per track)×(cylinder offset))+(sector number). This step ( 148 ) then provides the block offset to the return step where the starting block and block offset are provided. The block address can then be calculated by adding the starting block to the block offset.  
         [0038]    While the simplified table  40  and layout  42  do not show moving between areas in the middle of a track, this is also possible with the present invention. In such case, sector information could be added to the table  40  and additional processing added to the flow charts  100  and  130  to check for the sector to see which line or row of the table the desired address corresponds to.  
         [0039]    As can be appreciated, the present invention provides several advantages for producers of disk drive systems. Most importantly, every time a system is being designed, it is not necessary to write code that is particular to the layout. Instead, a generic set of code can be written that can be used in several different designs. This code can access a table that can be easily changed for different layouts.  
         [0040]    While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be appreciated by those skilled in the art that various other changes in the form and details may be made without departing from the spirit and scope of the invention. It should be understood that this description has been made by way of example, and that the invention is defined by the scope of the following claims.