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:
Sep. 09, 2003
Filed:
Oct. 31, 2000
Stephen J. Sicola, Colorado Springs, CO (US);
James Pherson, Colorado Springs, CO (US);
Jesse Yandell, Colorado Springs, CO (US);
Hewlett-Packard Development Company, L.P., Houston, TX (US);
Abstract
A system for generating a virtual point-in-time copy of a selected subset (e.g., a selected volume or logical unit) of a storage system. The present system operates by using a bitmap in storage system controller cache memory to indicate blocks of memory in the selected volume that have been overwritten since the snapshot was initiated. When a write to the selected volume is requested, the cache bitmap is checked to determine whether the original data (in the area to be overwritten) has already been copied from the selected volume to a temporary volume. If the original data was previously copied, then the write proceeds to the selected volume. If, however, the original data would be overwritten by the presently requested write operation, then an area containing the original data is copied from the selected volume to a temporary volume. Reads from the temporary volume first check the bitmap to determine if the requested data has already been copied from the selected volume to the temporary volume. If so, the data is read from the temporary volume, otherwise, the data is read from the selected volume.