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:
Jun. 30, 2009
Filed:
Sep. 23, 2003
Peter Bixby, Westborough, MA (US);
Sachin Mullick, Ashland, MA (US);
Jiannan Zheng, Ashland, MA (US);
Xiaoye Jiang, Shrewsbury, MA (US);
Sorin Faibish, Newton, MA (US);
Peter Bixby, Westborough, MA (US);
Sachin Mullick, Ashland, MA (US);
Jiannan Zheng, Ashland, MA (US);
Xiaoye Jiang, Shrewsbury, MA (US);
Sorin Faibish, Newton, MA (US);
EMC Corporation, Hopkinton, MA (US);
Abstract
Read-only and read-write snapshot copies of a production file in a Unix-based file system are organized as a version set of file inodes and shared file blocks. Version pointers and branch pointers link the inodes. Initially the production file can have all its blocks preallocated or it can be a sparse file having only an inode and its last data block. A protocol is provided for creating read-only and read-write snapshots, deleting snapshots, restoring the production file with a specified snapshot, refreshing a specified snapshot, and naming the snapshots. Block pointers are marked with a flag indicating whether or not the pointed-to block is owned by the parent inode. A non-owner marking is inherited by all of the block's descendants. The block ownership controls the copying of indirect blocks when writing to the production file, and also controls deallocation and passing of blocks when deleting a read-only snapshot.