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System and method for reallocating blocks in checkpointing bitmap-based file systems

  • US 8,370,301 B1
  • Filed: 06/12/2007
  • Issued: 02/05/2013
  • Est. Priority Date: 03/21/2003
  • Status: Active Grant
First Claim
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1. A method for operating a storage system, comprising:

  • maintaining a first portion of a storage operating system of the storage system for writing data to persistent storage operatively connected to the storage system;

    maintaining a second portion of the storage operating system for managing a plurality of bitmaps that track an allocation status of blocks of the persistent storage;

    maintaining a first bitmap of the plurality of bitmaps;

    maintaining a second bitmap comprising a first copy of the first bitmap;

    determining that the first portion is to write the first bitmap to the persistent storage while the second portion is to modify at least one of the first bitmap and the second bitmap;

    in response to determining that the first bitmap is to be written to the persistent storage while the second portion is to modify the at least one of the first bitmap and the second bitmap, creating a third bitmap comprising a second copy of the first bitmap;

    in response to creating the third bitmap, using the third bitmap by the first portion to be written to the persistent storage, and using the at least one of the first bitmap and the second bitmap by the second portion for modifications;

    executing a block allocation procedure to allocate a data block to the persistent storage;

    marking the data block as allocated in the first bitmap and the second bitmap; and

    waiting until the first portion finishes writing the data block to the persistent storage, and in response to finishing, discarding the third bitmap.

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