Version mapped incremental backups

摘要

A method to create a version map to represent the data state of a file at a particular point in time when an incremental backup is performed. In one embodiment, a logical memory backup file is created that is known as a cumulative data file. Changes to the cumulative data file according to one embodiment of the present invention include periodically appending copies of data modified since the prior backup. A new version map may be created each time an incremental backup occurs. Locations of both modified and unmodified data in the backup data file are mapped for future reference to the data.

主权项

1. A method comprising:
forming a full copy of data available for use by a computer system, wherein the full copy is formed in a logical memory; creating an initial map, wherein the initial map identifies locations in the logical memory of the full copy and an available storage portion; storing the initial map in memory; identifying a modified first portion of the data available for use by the computer system, wherein
the modified first portion comprises data which has been changed since a previous incremental backup operation, andthe modified first portion is based on an original first portion of data stored in the full copy; adding a copy of the modified first portion to the logical memory; maintaining the original first portion of data in the full copy unchanged since the forming of the full copy; creating a first map, wherein
the first map identifies locations in the logical memory of the full copy, and the copy of the modified first portion,the first map is tracks the location of the modified first portion in relation to the original first portion of data, wherein
the original first portion of data corresponds to the modified first portion, andthe creating the first map comprises
modifying a first extent specifier, wherein
the first extent specifier points to the end of a portion of data in the full copy that precedes the original first portion, in response to the modifying the first extent specifier,creating a second extent specifier, wherein
the second extent specifier points to a starting address of a subsequent portion of data that follows the original first portion in the full copy, andcreating a third extent specifier, wherein
the third extent specifier points to a starting address of the copy of the first modified portion; storing the first map in memory; adding a copy of a modified second portion of the data available for use by the computer system to the logical memory; creating a second map, wherein
the second map identifies locations in the logical memory of the full copy, the copy of the modified first portion, and the copy of the modified second portion,the second map comprises a plurality of extent specifiers, andeach extent specifier of the plurality of extent specifiers identifies a portion of the logical memory; storing the second map in memory, wherein
the initial map, the first map, and the second map are stored concurrently in memory; and reorganizing the extent specifiers to correspond to an order in which the portions of the logical memory are stored, wherein
the order facilitates restoration of a file using a single, linear pass of a storage medium.