Multi-way Checkpoints for Filesystem Data Integrity

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Solution Overview

Problem

Data storage systems face challenges in maintaining multiple checkpoint versions of a filesystem, where both the current and checkpoint versions may become corrupted, and important information may be lost or altered, with existing systems struggling to ensure data integrity and availability.

Innovation Solution

The method involves maintaining at least three superblocks in the data storage system, each representing a version of the filesystem, including a working version and two checkpoint versions, with indirection objects referenced by these superblocks, allowing for the retention of a new checkpoint version while continuing to manage the filesystem using a separate superblock, thereby ensuring data integrity and availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If only two superblocks are maintained (one current, one checkpoint), then device complexity is reduced, but data integrity and reliability deteriorate because both versions may become corrupted or important information may be lost

Engineering Contradiction:

Improvedata integrityVSAvoidnumber of superblocks

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The filesystem metadata structure is segmented into multiple independent superblocks (at least three: current, first checkpoint, second checkpoint) instead of using a single or dual superblock system. Each superblock maintains separate filesystem state information, allowing independent validation and recovery paths.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different superblocks serve different functional roles with specialized purposes: the current superblock for active filesystem operations, and checkpoint superblocks for preserved historical states. This local specialization allows optimized handling of each superblock type.

Inventive Principle:

Principle #3Local quality

2Reliability

If multiple checkpoint versions are maintained, then data integrity is improved, but device complexity increases due to managing multiple superblocks and indirection objects

Engineering Contradiction:

Improvefilesystem recoveryVSAvoidsuperblock management

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

An indirection object is introduced as an intermediary data structure that manages references to multiple superblocks. This indirection layer abstracts the complexity of managing multiple checkpoint versions, providing a unified interface for accessing different filesystem states without requiring direct management of each superblock.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system adds a temporal dimension to superblock management by maintaining multiple versions across different time points (current and historical checkpoints). This multi-dimensional approach allows recovery to any previous state while organizing complexity in a structured temporal sequence.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of operation

If two superblocks are used for current and checkpoint versions, then ease of operation is maintained, but the risk of simultaneous corruption increases

Engineering Contradiction:

Improvefilesystem managementVSAvoidcorruption risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The system maintains multiple checkpoint superblocks as preventive cushions against data loss. By preserving at least two checkpoint versions in addition to the current superblock, the system creates buffer layers that protect against simultaneous corruption events, ensuring recovery capability even when some superblocks are compromised.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Reliability

If more than two superblocks are maintained, then data availability is improved through multiple recovery points, but storage overhead increases

Engineering Contradiction:

Improverecovery pointsVSAvoidstorage overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system implements a lifecycle management approach where checkpoint superblocks are maintained for a defined period and then discarded or archived. This allows the system to provide multiple recovery points while managing storage overhead by periodically cleaning up older checkpoints that are no longer needed for recovery.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS9767120B2Multi-way checkpoints in a data storage system

Publication Date: 2017.09.19 HITACHI VANTARA LLC

AI summary

Embodiments of the present invention allow multiple checkpoints to be taken so that multiple versions of the filesystem, including a working version and at least two checkpoint versions, can be maintained over time. Specifically, at least three “superblock” root structures are used to manage multiple instantiations of the filesystem. The superblocks are preferably stored in fixed locations within the storage system for easy access, although they may alternatively be stored in other ways. The number of superblocks may be fixed or variable.