System for generating a point-in-time copy of data in a data storage system
October 31, 2020. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesFault tolerant computer backup system System to reformat images for three-dimensional display using unique spatial encoding and non-planar bisectioning Method and system for incremental time zero backup copying of data Method and apparatus for cache memory management using a two level scheme including a bit mapped cache buffer history table and circular cache buffer list Method for maintaining consistent states of a file system and for creating user-accessible read-only copies of a file system Method, software and apparatus for saving, using and recovering data RE37038 Method, software and apparatus for saving, using and recovering data Method and apparatus for managing copy on write operations in a virtual memory Method software and apparatus for saving using and recovering data InventorsAssigneeApplicationNo. 09/702575 filed on 10/31/2000US Classes:711/154, Control technique707/201, Coherency (e.g., same view to multiple users)707/202, Recoverability707/203, Version management707/204, Archiving or backup711/114, Arrayed (e.g., RAIDs)711/161, Archiving711/162, Backup714/15, State recovery (i.e., process or data file)714/20, Plural recovery data sets containing set interrelation data (e.g., time values or log record numbers)714/6Redundant stored data accessed (e.g., duplicated data, error correction coded data, or other parity-type data)ExaminersPrimary: Kim, MatthewAssistant: Elmore, Stephen C. International ClassG06F 11/14 (20060101)AbstractA 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. | |
