Efficient backup of multiple versions of a file using data de-duplication

A non-transitory computer-readable storage medium having computer-executable instructions stored thereon that, when executed by a computer, cause the computer to:

• read a block of data from a current version of a data file;
• determine if the size of the block of data is less than a block size;
• upon determining that the block of data is not less than the block size, determine if a unique data block having matching data exists in a master file corresponding to the data file;
• upon determining that a unique data block having matching data exists in the master file, append a reference to the unique block having matching data in the master file to an anterior file corresponding to the current version of the data file;
• upon determining that a unique data block having matching data does not exist in the master file, append the block of data to the master file and append a reference to the appended block of data in the master file to the anterior file corresponding to the current version of the data file;
• upon determining that the block of data is less than the block size, write the block of data to a posterior file corresponding to the current version of the data file, the last block of data being a portion of the data file less than the block size;
• maintain a reference count for each of the unique data blocks in the master file in a reference block file corresponding to the data file, wherein the reference count for each unique data block indicates a number of times the unique data block is referenced in all anterior files corresponding to all backed-up versions of the data file;
• upon determining that a unique data block having matching data does not exist in the master file, determine if a unique data block location having a corresponding reference count in the reference block file with a value of zero exists in the master file;
• and
• upon determining that a unique data block location having a corresponding reference count with a value of zero exists in the master file, copy the data from the block of data to the unique data block location, append a reference to the unique data block location to the anterior file corresponding to the current version of the data file, and increment the reference count corresponding to the unique data block location in the reference block file, wherein the unique data block location is a previously allocated portion of the master file storing a unique block of data associated with a deleted version of the data file.

A system for backing-up multiple versions of a data file stored on a storage volume to a backup location, the system comprising:

• a user computer comprising a processor and a memory operatively coupled to the processor;
• and
• a continuous data protection (“CDP”) module executing in the processor from the memory and that, when executed by the processor, causes the user computer to:
• detect a modification to the data file stored on the storage volume,
• copy one or more unique data blocks of a specific block size from a current version of the data file to a master file corresponding to the data file in the backup location,
• create an anterior file in the backup location for the current version of the data file containing an ordered list of references to the one or more unique data blocks of the specific block size in the master file, wherein the ordered list of references is based on the order of occurrence of each unique data block in the current version of the data file,
• write a last block of data in the data file to a posterior file corresponding to the current version of the data file, wherein the last block of data is a portion of the data file less than the specific block size, and the posterior file is maintained in the backup location, and
• maintain a reference count for each of the one or more unique data blocks in the master file in a reference block file corresponding to the data file, wherein the reference count for each unique data block indicates a number of times the unique data block is referenced in all anterior files corresponding to all backed-up versions of the data file, wherein copying one or more unique data blocks of a specific block size from the data file to a master file corresponding to the data file comprises copying at least one data block from the data file to a unique data block location in the master file having a corresponding reference count in the reference block file with a value of zero, and wherein the unique data block location is a previously allocated portion of the master file storing a unique block of data associated with a deleted version of the data file.