06792518 is referenced by 171 patents.

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.

Title
Data storage system having mata bit maps for indicating whether data blocks are invalid in snapshot copies
Application Number
10/213241
Publication Number
6792518 (B2)
Application Date
August 6, 2002
Publication Date
September 14, 2004
Inventor
Himabindu Tummala
South Grafton
MA, US
Philippe Armangau
Acton
MA, US
Agent
Novak Druce
US
Agent
Richard C Auchterlonie
US
Assignee
EMC Corporation
MA, US
IPC
G06F 12/00
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