Patent Publication Number: US-2012030510-A1

Title: Method to recover data sector damaged by abrupt power loss in hard disk drives

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a power loss event in a hard disk drive. 
     2. Background Information 
     Hard disk drives are used to store data within a system. In the event of sudden power loss, for example when a user pulls the plug on an operating system, the system will include components that allow for writing of data within the disk drive. For example, the system may include a capacitor that stores enough energy to allow the drive to complete the writing of a disk sector. Such an approach is adequate for drives that have 512 byte sectors. If the sectors are expanded, for example to 4 Kbytes per sector, then such capacitors would not have enough power to allow the drive to write a complete sector or mark potentially corrupt sectors. 
     BRIEF SUMMARY OF THE INVENTION 
     A hard disk drive that is connected to a non-volatile memory that includes data stored upon the occurrence of a power loss, the data having been designated to be stored in the hard disk drive in a previous time period. The hard disk drive includes a circuit that causes the data stored in the non-volatile memory to be written onto a disk of the drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of an embodiment of a hard disk drive; 
         FIG. 2  is a schematic of an electrical circuit for the hard disk drive; 
         FIG. 3  is a schematic showing a system with a processor, hard disk drive and non-volatile memory; 
         FIG. 4  is a flowchart showing a write operation of the hard disk drive; and, 
         FIG. 5  is a flowchart showing a hard disk drive process when power is turned on. 
     
    
    
     DETAILED DESCRIPTION 
     Described is a hard disk drive that is coupled to a non-volatile memory. The non-volatile memory includes data that was designated to be stored in the hard disk drive in a previous time period. When a power loss event is detected the hard disk drive stores the track address of the last written track in non-volatile memory. When power is returned, the hard drive retrieves the last track address from the non-volatile memory. The data can then be rewritten onto the last track. Such an approach allows relatively large sectors of 4 Kbytes to be recaptured after a power loss event. 
     Referring to the drawings more particularly by reference numbers,  FIG. 1  shows an embodiment of a hard disk drive  10 . The disk drive  10  may include one or more magnetic disks  12  that are rotated by a spindle motor  14 . The spindle motor  14  may be mounted to a base plate  16 . The disk drive  10  may further have a cover  18  that encloses the disks  12 . 
     The disk drive  10  may include a plurality of heads  20  located adjacent to the disks  12 . Each head  20  may have separate write and read elements. The write element magnetizes the disk  12  to write data. The read element senses the magnetic fields of the disks  12  to read data. By way of example, the read element may be constructed from a magneto-resistive material that has a resistance which varies linearly with changes in magnetic flux. 
     Each head  20  may be gimbal mounted to a suspension arm  26  as part of a head gimbal assembly (HGA). The suspension arms  26  are attached to an actuator arm  28  that is pivotally mounted to the base plate  16  by a bearing assembly  30 . A voice coil  32  is attached to the actuator arm  28 . The voice coil  32  is coupled to a magnet assembly  34  to create a voice coil motor (VCM)  36 . Providing a current to the voice coil  32  will create a torque that swings the actuator arm  28  and moves the heads  20  across the disks  12 . 
     The hard disk drive  10  may include a printed circuit board assembly  38  that includes one or more integrated circuits  40  coupled to a printed circuit board  42 . The printed circuit board  40  is coupled to the voice coil  32 , heads  20  and spindle motor  14  by wires (not shown). 
       FIG. 2  shows an electrical circuit  50  for reading and writing data onto the disks  12 . The circuit  50  may include a pre-amplifier circuit  52  that is coupled to the heads  20 . The pre-amplifier circuit  52  has a read data channel  54  and a write data channel  56  that are connected to a read/write channel circuit  58 . The pre-amplifier  52  also has a read/write enable gate  60  connected to a controller  64 . Data can be written onto the disks  12 , or read from the disks  12  by enabling the read/write enable gate  60 . 
     The read/write channel circuit  58  is connected to a controller  64  through read and write channels  66  and  68 , respectively, and read and write gates  70  and  72 , respectively. The read gate  70  is enabled when data is to be read from the disks  12 . The write gate  72  is enabled when writing data to the disks  12 . The controller  64  may be a digital signal processor that operates in accordance with a software routine, including a routine(s) to write and read data from the disks  12 . The read/write channel circuit  58  and controller  64  may also be connected to a motor control circuit  74  which controls the voice coil motor  36 , and spindle motor  14  of the disk drive  10 . The controller  64  may be connected to a non-volatile memory device  76 . By way of example, the device  76  may be a read-only memory (“ROM”) that contains instructions that are read by the controller  64 . 
       FIG. 3  shows a system  100  that includes a hard disk drive  10 , a processor  102  and a non-volatile memory  104 . The drive  10 , processor  102  and non-volatile memory  104  are coupled together by one or more busses  106  as is known in the art. By way of example, the non-volatile memory  104  may be a flash memory device. The processor  102  may operate software routines in accordance with instructions and data as is known in the art. 
       FIG. 4  shows a flowchart of a write operation within the disk drive. The drive initiates a write operation in block  110 . In block  112  a write power fault flag is set to zero and a write power fault interrupt is enabled. The interrupt can be provided by the external processor to the disk drive. Data is written onto the disk in block  114  and decision block  116 . A power loss may be detected which causes a power fault interrupt by the processor in block  118 . The track address for the data being written in the drive is saved in the non-volatile memory in block  120 . block  122  the write power fault flag is set to one. 
     Decision block  116  determines if there is a power fault interrupt. If no, the writing process continues. If yes, the method continues to block  124  where the power write fault interrupt within the drive is disabled. The value of the write power fault flag is determined in decision block  126 . If the flag is zero the process completes the writing process and ends. If the flag is set at 1 then the data saved in the non-volatile memory is removed in block  128  and the write process continues. A flag setting of 1 in this process indicates that an interrupt occurred but power was not lost. By way of example, steps  118 - 122  may be performed by the processor and the remaining steps may be performed by the disk drive controller. 
       FIG. 5  is a flowchart showing a process that occurs within the disk drive when power is turned back on. The non-volatile memory is examined in block  132 . Decision block  134  determines whether the non-volatile memory includes the track address of the data that was being stored during a power loss event. If not, then the process ends. If the non-volatile memory contains the track address the drive reads the corresponding track in block  136 . It is determined whether there is an error in the track in decision block  138 . If there is an error, the data can be rewritten onto the disk in block  140 . If there is no error the track address and data are removed from the non-volatile memory in block  142 . These steps may be performed by the disk drive controller. 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.