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Cache for optical storage device and method for implementing same

  • US 5,588,129 A
  • Filed: 01/16/1996
  • Issued: 12/24/1996
  • Est. Priority Date: 02/09/1994
  • Status: Expired due to Term
First Claim
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1. A cache apparatus for storing data for a plurality of optical disk storage media alternatively loadable into a common optical disk drive, the apparatus comprising:

  • volatile memory and non-volatile memory for storing disk data read from the plurality of optical disk storage media, the volatile memory serving as a primary cache and the non-volatile memory serving as a secondary cache, the secondary cache comprising a portion of aa plurality to a respective optical disk identification codes stored in non-volatile memory and corresponding to a plurality of optical disk storage media alternatively loadable into the common optical disk drive, each identification code unique to a corresponding optical disk storage media;

    an index stored in non-volatile memory pointing among said plurality of identification codes to a currently accessible optical disk storage media;

    a first data structure stored in non-volatile memory for mapping at least a portion of said disk data stored in the non-volatile memory to corresponding address locations on an associated optical disk storage media, said first data structure comprising a first tag associated with first disk data read from a first optical disk storage media and a second tag associated with second disk data read from a second optical disk storage media; and

    a digital processing means allocating the nonvolatile memory no comprise;

    a second data structure for storing disk data, the stored disk data in the second data structure being organized into a plurality of groups of disk data, and wherein only one group of the plurality of groups of disk data is active at one time, each one group being a physically contiguous sector area within the non-volatile memory;

    a third data structure for storing a plurality of markers and a corresponding plurality of optical disk sector addresses, each marker of said plurality of markers corresponding to a group ofsaid plurality of grouses of cached data; and

    the digital processing means allocating the volatile memory to comprise a fourth data structure for storing a portion of the disk data stored in the second data structure of the nonvolatile memory;

    the digital processing means processing a request to read disk data from an optical disk storage media fin a and comprising.(i) means for defining the index pointing among said plurality of identification codes which corresponds to a current optical disk storage media;

    (ii) means for accessing the first data structure to identify whether disk data is stored in non-volatile memory; and

    (iii) means for retrieving first disk data from said non volatile memory without first re-storing said first disk data from said first optical disk storage media into the non-volatile memory following changes in the current optical disk storage media away from the first optical disk storage media and back to the first optical disk storage media, when said disk data is stored in said non-volatile memory; and

    said digital processing means executing a first computer program for covering stored disk data after a restoration of power, and further comprising;

    (iv) means for determining one marker of the plurality of markers as being invalid and each other marker of the plurality of markers as being valid by scanning among the plurality of markers to identify a last valid marker before said one invalid marker;

    (v) means for defining a next marker unique to all valid markers in said third data structure, wherein said next marker is an increment of said last valid marker;

    (vi) means for deriving a next location in the second data structure corresponding to said next marker for storing disk data.

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