Abstract:
When a disk sector is written to, a bit for the sector is set indicating that the sector will require secure data disposal (SDD) to be run on it. To save time during end of life disposal, SDD is executed only on sectors whose bits indicate that they have been written to. SDD can be executed on each dirty sector in one operation at end of life or incrementally during use as disk activity permits.

Description:
This is a continuation of and claims priority from U.S. patent application Ser. No. 12/028,114, filed Feb. 8, 2008. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to secure data disposal (SDD) for disk drives. 
     BACKGROUND OF THE INVENTION 
     During the retirement phase of the PC life cycle, many users dispose of PCs without properly removing confidential data. This is a serious concern, since the information on these hard disks can then be retrieved by unauthorized people. 
     Many users think that formatting a hard disk removes and destroys its data, when in fact this data, which can be highly confidential, can still be retrieved from these systems. With most operating systems, files that are deleted are not necessarily erased. In many cases, the only thing erased is the logical link to the file. 
     SUMMARY OF THE INVENTION 
     To ensure that data cannot be retrieved even if a disk is removed from the drive and residual magnetic fields read by sophisticated data thieves, SDD is executed only on data regions that have been written to at least once during the lifetime of a disk drive, in some hard disk drive implementations up to fourteen overwrite cycles maybe conducted as part of the SDD to ensure that any residual magnetic fields from the original data write are effectively eliminated, but as understood herein, absent present principles over twenty four hours may be required for such a comprehensive and repetitive overwrite process. 
     A method is disclosed for secure data disposal (SDD) of a disk drive having at least one data storage disk defining data regions. The method includes, for each data region to which data is written, indicating that the data region has been written to. The method then includes executing SDD only of data regions indicated to have been written to, and not executing SDD in data regions that have never been written to. 
     SDD may be executed only at end of life of the disk drive but only on all data regions indicated as having been written to at least once. Alternatively, SDD may be executed during operational life of the disk drive, e.g., on a previously written data region immediately after the previously written data region is indicated as being a free data region, or on a previously written data region during an idle period of the drive subsequent to an indication that the previously written data region is a free data region. 
     In one example, the data region can be a disk sector and the SDD includes writing a first pattern into substantially all bit locations of a sector, then writing at least a second pattern different from the first pattern into substantially all hit locations of the same sector. For sonic hard disk drive applications up to fourteen patterns may be written one on top of the other. 
     In another aspect, a tangible computer readable medium bears instructions to cause a processor, when a data storage disk sector is written to, to set a bit for the sector indicating that the sector will require secure data disposal (SDD) to be run on it. The processor executes SDD only on sectors whose bits indicate that they have been written to. 
     In another aspect, a disk drive includes one or more data storage disks and a processor writing data to sectors of the disk. A tangible program storage device bears instructions to cause the processor, pursuant to writing data to a sector, to set an indicator bit associated with the sector indicating that data has been written thereto. The instructions also cause the processor to execute secure data disposal (SDD) only on sectors whose respective indicator bits indicate the sectors have been written to. 
     In another aspect, a disk drive includes one or more data storage disks and a processor writing data to sectors of the disk. A tangible program storage device hears instructions to cause the processor, pursuant to writing data to a sector, determine whether another sector has been designated as being a free sector as a result. The instructions cause the processor to execute secure data disposal (SDD) only on the free sector. 
     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one non-limiting system in accordance with present principles; 
         FIG. 2  is a flow chart of one example logic that may be employed in accordance with present principles; and 
         FIG. 3  is a flow chart of another example logic; that may be employed in accordance with present principles. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to  FIG. 1 , a disk drive  10  such as, in one example, a hard disk drive can be used by a host computer  12  such as a notebook computer or desk top computer or any device that uses a disk drive to store data. The disk drive  10  typically includes a drive controller  14  that can be implemented by a processor. The disk drive  10  also includes a tangible computer readable medium such as but not limited to a solid state data cache  16  that, among other things, can store logic disclosed herein. The logic is executable by the drive controller  14  or other processor in the disk drive  10 . 
     The controller  14  can also control one or more head position mechanisms  18  that move one or more suspensions  20  bearing read and write heads  22 . The heads  22  read information from and write information to one or more rotatable data storage disks  24 . Typically, data is written to discrete areas of the disk  24  referred to herein as “sectors”  26 , it being understood that “sector” is not limited to a particular geometry such as a ring or wedge but more generally refers to a portion of the disk  24  that is regarded as a discrete storage area unit for purposes of secure data disposal (SDD). 
     SDD typically involves writing plural unique patterns of “ones” and “zeroes” into each sector of the disk, one pattern on top of another. More specifically, a first pattern is written into substantially all bit locations of a sector, then at least a second pattern different from the first is written into substantially all bit locations of the same sector to effect SDD. Additional patterns may be overwritten on top of the first two if desired. This is true of hard disk drives and other storages that rely on magnetic principles to store data. In the case of optical drives, flash memory, and other true digital devices, only one overwrite pattern may be required. 
       FIG. 2  shows one embodiment of logic that may be implemented in accordance with present principles. Commencing at block  28 , for each new drive, each sector is designated as “clean”, i.e., as never having been written. This designation may be accomplished by establishing the value of an indicator bit, referred to herein for convenience as a SDD bit, as appropriate, e.g., to be “zero” for “clean” and “one” for “dirty”. The SDD bit for sector may reside in the sector or it may reside elsewhere, e.g., in a SDD bit table stored in the cache  16 . 
     The drive, is then sold for use and subsequently during its operational lifetime, at block  30  for each write to a sector the SDD bit of the sector is set to a value indicating “dirty” at block  32 . At the end of the operational life of the disk drive when it is intended to be securely disposed of at block  34 , for each sector at block  36  it is determined at decision diamond  38  whether the respective SDD bit indicates that the sector is dirty. If it does, SDD is executed on the sector at block  40 , and upon completion of SDD the next sector is retrieved for test at block  42 , with the logic looping back to decision diamond  38  to test the SDD bit of the next sector. On the other hand, if the test at decision diamond  38  is negative, SDD is not executed on the sector, and the logic proceeds immediately to block  42 . In this way, SDD is performed only on sectors requiring it, saving execution time. 
     An alternate implementation is shown in  FIG. 3 . Commencing at block  44 , for each new drive, each sector is designated as “clean”, i.e., as never having been written. This designation may be accomplished by establishing the value of an indicator bit, referred to herein for convenience as a SDD bit, as appropriate, e.g to be “zero” for “clean” and “one” for “dirty”, The SDD bit for a sector may reside in the sector or it may reside elsewhere, e.g., in a SDD bit table stored in the cache  16 . 
     The drive is then sold for use and subsequently during its operational lifetime, at block  46  for each write to a sector the SDD bit of the sector is set to a value indicating “dirty” at block  48 . However, unlike the logic of  FIG. 2 , the logic of  FIG. 3  implements SDD during the operational life of the disk to further reduce the amount of time required at end of life to secure the disk. 
     Specifically, when a write is executed, a previously written sector might be designated as being “free” as a result when, for instance, data in the previously written sector is updated but owing to space constraints the updated version, is written into another sector. When this occurs at decision diamond  50 , SDD is executed on the newly freed sector at block  52  and the SDD bit reset to “clean” at block  54 . SDD may be executed on the free sector immediately after the free sector is indicated as being a free sector, or SDD can be executed on the free sector during the next subsequent idle period of the drive after the free sector has been designated as such. 
     While the particular SECURE DATA DISPOSAL FOR DISK DRIVE is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.