N Series Snapshot: A Technical Discussion
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Overview: This IBM paper discusses the N series Snapshot feature. Snapshot is a standard feature of the Data ONTAP operating system. It enables online backups to be maintained, thus providing near-instantaneous access to previous versions of data without requiring complete, separate copies or resorting to offline backups. The paper focuses on the algorithms and data structures that Write Anywhere File Layout (WAFL) uses to implement Snapshots, which are read-only clones of the active file system. It also describes how WAFL uses Snapshots to eliminate the need for file system consistency checking after an unclean shutdown.