Snapshot Longevity Ranking for Storage Space Reclamation

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Solution Overview

Problem

Conventional snapshot management systems face inefficiencies in reclaiming storage space for overwritten or deleted data, leading to performance issues due to the lack of effective methods for transferring ownership of uniquely-written data during snapshot deletion.

Innovation Solution

A snapshot management system utilizes longevity ranking values to determine which snapshot node should assume ownership of uniquely-written data, minimizing metadata modifications and optimizing storage space reclamation by selecting the node with the highest expected lifespan to transfer ownership.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If conventional techniques are used to reclaim storage space from sparsely-populated snapshots, then storage space can be recovered, but system performance deteriorates due to inefficient reclamation processes

Engineering Contradiction:

Improvestorage space reclamationVSAvoidsystem performance

Core Design Contradiction:

Loss of substanceVSProductivity

Solution Approach 1:

The system pre-calculates and stores longevity ranking values for each snapshot volume node before deletion occurs. When a snapshot is deleted, the system immediately references these pre-computed values to determine the optimal candidate for data ownership transfer, eliminating the need for complex real-time analysis and thus maintaining high system performance during space reclamation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Each snapshot volume node maintains its own longevity ranking value that automatically reflects its expected lifespan based on the snapshot tree structure and deletion patterns. This self-maintained metadata allows the system to make autonomous decisions about data ownership transfer without requiring external intervention or complex coordination, improving reclamation efficiency

Inventive Principle:

Principle #25Self-service

2Reliability

If all data of a source volume is duplicated at snapshot creation, then complete data redundancy is achieved, but storage space efficiency deteriorates

Engineering Contradiction:

Improvedata redundancyVSAvoidstorage space utilization

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The snapshot storage structure is segmented into two distinct components: uniquely-written data specific to each snapshot and shared data inherited from parent snapshots or the original volume. This segmentation allows the system to store only the minimal necessary data in each snapshot while maintaining complete data redundancy through the hierarchical relationship structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a nested snapshot tree structure where child snapshots contain only their unique data changes, while parent snapshots or the original volume contain the base data. This nesting allows snapshots to be embedded within a hierarchical structure, achieving complete data redundancy without duplicating entire data sets at each level

Inventive Principle:

Principle #7Nested doll (Nesting)

3Quantity of substance

If snapshots store only uniquely-written data with metadata redirection, then storage space efficiency is improved, but complexity of managing data ownership and redirection increases

Engineering Contradiction:

Improvestorage space efficiencyVSAvoidmetadata management complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The system introduces a new parameter - longevity ranking value - that quantifies the expected lifespan of each snapshot volume node. This parameter transformation converts the complex qualitative assessment of snapshot importance into a simple numerical metric, enabling automated decision-making about data ownership transfer and reducing the complexity of metadata management

Inventive Principle:

Principle #35Parameter changes

4Ease of operation

If snapshot deletion is allowed without restrictions, then user flexibility is improved, but data integrity of dependent snapshots may deteriorate

Engineering Contradiction:

Improvesnapshot deletion flexibilityVSAvoiddata integrity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system implements a feedback mechanism where the longevity ranking values and snapshot dependency relationships are continuously monitored. When a deletion request occurs, the system automatically queries this feedback information to determine if the deletion would compromise data integrity, and only permits deletion when it is safe to do so, thus maintaining both user flexibility and data integrity

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11372810B2Storage system implementing snapshot longevity ranking for efficient management of snapshots

Publication Date: 2022.06.28 EMC IP HLDG CO LLC

AI summary

Techniques are provided for utilizing snapshot longevity information to manage snapshots of storage volumes in a snapshot-enabled storage system. A snapshot management system maintains a snapshot volume tree which comprises a plurality of snapshots having respective longevity ranking values. The longevity ranking value of a given snapshot represents an expected life span of the given snapshot as compared to expected life spans of other snapshots as indicated by their respective longevity ranking values. When a snapshot is deleted, the snapshot management system determines a set of candidate snapshots which can assume ownership of uniquely-written data of the deleted snapshot, evaluates the longevity ranking values of the candidate snapshots to select a candidate snapshot to assume ownership of the uniquely-written data of the deleted snapshot, and modifies metadata of the selected snapshot to transfer the ownership of the uniquely-written data from the deleted snapshot to the selected snapshot.