Data storage system having mata bit maps for indicating whether data blocks are invalid in snapshot copies
US6792518B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 6, 2002 |
| Grant date | Sep 14, 2004 |
| Priority date | — |
| Expiry date | Mar 19, 2023 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S707/99954
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
In a data storage system providing access to a production dataset and snapshot copies of the production dataset, a production meta bit map identifies blocks of storage that are invalid in the production dataset. If a block in the production dataset is invalid when a snapshot copy is being made, then there is no need to copy the block to storage for the snapshot before writing to the block. Moreover, if a block in the production dataset supporting a snapshot copy is dynamically invalidated, it may be kept in the production dataset until it is written to. For this purpose, a respective snapshot copy of the meta bit map is made and kept with each of the snapshot datasets, and the snapshot copies of the meta bit map are merged in order to indicate the blocks that are invalid for all of the snapshots.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.