OPTIMIZATION TO PERMIT BLOCK BASED INCREMENTAL BACKUP ACROSS SYSTEM REBOOT OR CRASH

摘要

Techniques to back up data are disclosed. In various embodiments, a copy of a free block map as of a first time associated with a first backup is stored in persistent data storage. Writes made subsequent to the first backup to blocks not listed as free in the copy of the free block map as of the first time are tracked in a persistently-stored change block tracking log. A free block map as of a second time and the previously-stored copy of the free block map as of the first time are used to determine which blocks listed as free in the free block map as of the first time have been written to since the first time. At least a subset of blocks determined to have been written to since the first time are including in an incremental backup.

主权项

1. A method, comprising:
storing in data storage a free block map as of a first time associated with a first backup; in response to the first backup,
tracking, in a change block log, a modification to one or more blocks that is modified subsequent to the first backup, wherein tracking the modification to the one or more blocks comprises:
tracking the modification to the one or blocks based at least in part on whether the one or more blocks correspond to one or more blocks in the free block map are identified as free, such that the modification to the one or more blocks is tracked if the one or more blocks correspond to one or more blocks in the free block map as of the first time that were not identified as free; determining that an incremental backup is to be performed at a second time subsequent to the first time; and performing the incremental backup based at least in part on the change block log.