Directory-Level Snapshots Using Inode Identity Maps

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Solution Overview

Problem

Conventional volume-level snapshots are inadequate for scale-out architectures where different clients have varying data management and snapshot requirements, leading to inefficiencies and unsuitable data protection.

Innovation Solution

Implementing directory-level snapshots using an inode identity map to track inode numbers and create snapshots at a directory level, allowing for granular management and efficient storage operations, including on-demand snapshots and block-level granularity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If volume-level snapshots are implemented for data protection, then data loss protection is achieved, but storage efficiency and client-specific customization are reduced

Engineering Contradiction:

Improvedata loss protectionVSAvoidclient-specific snapshot requirements

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the volume-level snapshot functionality into directory-level snapshots, allowing different clients to have snapshots of specific directories rather than entire volumes. This enables customization for each client's needs while maintaining data protection, directly resolving the contradiction between reliability and adaptability.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If directory-level snapshots are implemented, then storage efficiency and client-specific management are improved, but system complexity increases

Engineering Contradiction:

Improvegranular data managementVSAvoidsnapshot management system

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces an inode identity map as an intermediary data structure that tracks inode numbers across snapshots. This intermediary mechanism simplifies the complexity of directory-level snapshot management by providing a straightforward method to identify and manage file versions without requiring complex tracking systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of substance

If incremental snapshots are created for each client, then storage space efficiency is improved, but snapshot creation and management overhead increases

Engineering Contradiction:

Improvestorage space consumptionVSAvoidsnapshot creation speed

Core Design Contradiction:

Loss of substanceVSProductivity

Solution Approach 1:

The patent makes the inode identity map a universal mechanism that serves multiple functions: tracking inode numbers, identifying incremental changes, and enabling efficient snapshot creation. This multi-functional approach allows incremental snapshots to be created efficiently across multiple clients simultaneously, resolving the contradiction between storage efficiency and productivity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250370958A1Directory snapshot and data management

Publication Date: 2025.12.04 NETAPP INC

AI summary

Techniques are provided for directory snapshot and data management. Conventional snapshot functionality creates snapshots at a volume level. Volume level snapshots are inadequate for scale-out storage architectures because a single volume snapshot of a shared storage resource may not satisfy different data protection requirements of clients using the shared storage resource. The disclosed techniques are capable of creating snapshots at a directory level. The directory level snapshots are created and maintained using an inode identity map to track active inode numbers of directory files that have diverged. Snapshot generation numbers are used to determine whether a file is part of a directory for which snapshotting is enabled. A version map used to track versions of a file modified across different directory snapshots and an active file system. A delayed free metafile is used to determine whether file block numbers of a directory can be freed.