The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 17, 2009
Filed:
Sep. 15, 2004
John Kemeny, Westford, MA (US);
Michael R. Mccarthy, Mansfield, MA (US);
Bradford B. Glade, Harvard, MA (US);
David Harvey, Newton, MA (US);
James A. Wentworth, Iii, Shrewsbury, MA (US);
William B. Whalen, Shrewsbury, MA (US);
Matthew Waxman, Brookline, MA (US);
John Kemeny, Westford, MA (US);
Michael R. McCarthy, Mansfield, MA (US);
Bradford B. Glade, Harvard, MA (US);
David Harvey, Newton, MA (US);
James A. Wentworth, III, Shrewsbury, MA (US);
William B. Whalen, Shrewsbury, MA (US);
Matthew Waxman, Brookline, MA (US);
EMC Corporation, Hopkinton, MA (US);
Abstract
A point in time copy of a data set is provided using a two-phase snapshot copy operation. When a write request is received, as part of the first phase, a chunk including the target location of the write request is determined. Using a 'copy on first write' technique, the data at the target location is copied to a snap data area in an allocated data area that is the size of the chunk. A first map for the data set is updated to include up to three entries representing a mapping of the segment including the target location. A second map for the snap data area is updated to include a single entry for the copy of the data from the target location. As part of the second phase, the multiple entries in the first map are coalesced into a single entry after the remaining portions of the chunk are copied to the data area in the snap data area.