Flash-Aware Snapshot Technique for Data Recovery

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Solution Overview

Problem

Traditional snapshot techniques for flash-based storage systems are limited by high write operations and storage space requirements, and they do not guarantee data recovery when the backup site is down, as they often rely on full-clone snapshots that are expensive to maintain and require large storage capacity.

Innovation Solution

A flash-aware snapshot technique that uses a commutative binary operator, such as an exclusive OR operator, to generate combined snapshots from prior and current snapshots, allowing for data recovery even if the production or backup site is inoperative, while reducing storage space requirements by exploiting content locality and compressing data with zero bits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If full-clone snapshots are used for data recovery, then data recovery reliability is improved, but storage space requirements and write operations increase significantly

Engineering Contradiction:

Improvedata recovery reliabilityVSAvoidstorage space requirements

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent segments the snapshot data into two separate volumes: a first snapshot volume storing only the data present at the snapshot time instance, and a second snapshot volume storing only the changes (delta) from that time instance. This segmentation allows the system to maintain complete snapshot capability while reducing storage requirements compared to full-clone snapshots that store all data.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges the first snapshot volume and second snapshot volume during data recovery operations. The memory controller combines data from both volumes to reconstruct the complete snapshot state, achieving full data recovery capability without requiring full-clone snapshot storage space.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If full-clone snapshots are generated periodically, then data recovery capability is improved, but time consumption and storage space increase

Engineering Contradiction:

Improvedata recovery capabilityVSAvoidtime consumption for snapshot generation

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

By segmenting snapshot data into base data (first volume) and change data (second volume), the system only needs to track and store changes rather than copying entire datasets periodically. This dramatically reduces the time required for snapshot generation while maintaining complete recovery capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of performing full data copying for each snapshot (excessive action), the system performs only partial copying of changed data blocks. This partial action approach reduces snapshot generation time and storage overhead while maintaining complete data recovery capability through the combination of both volumes.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If COW or ROW snapshot techniques are used, then storage space is reduced compared to full-clone snapshots, but data recovery is not guaranteed when backup site is down

Engineering Contradiction:

Improvestorage spaceVSAvoiddata recovery guarantee

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent prepares both the first snapshot volume and second snapshot volume in advance and maintains them in a ready state. By pre-positioning both the base snapshot data and the change data in separate volumes, the system ensures that data recovery can proceed using only local storage resources even when the backup site is unavailable, providing beforehand cushioning against site failures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The system creates a complete functional copy of the snapshot capability by maintaining two separate volumes that together contain all necessary data. The first volume contains the base snapshot and the second volume contains the changes, and their combination provides a complete copy of the snapshot state that can be recovered independently of the backup site.

Inventive Principle:

Principle #26Copying

4Device complexity

If traditional snapshot techniques are used, then implementation simplicity is maintained, but write operations and storage requirements are high

Engineering Contradiction:

Improveimplementation simplicityVSAvoidwrite operations efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent segments snapshot management into two distinct volume types with clear functional separation. The memory controller uses straightforward logic to determine which volume to read from or write to based on the operation type, maintaining implementation simplicity while improving write efficiency by avoiding redundant full-data copying.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9535799B2Apparatus, systems, and methods for data recovery

Publication Date: 2017.01.03 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

The embodiments disclosed herein provide a flash aware snapshot technique for two-way data recovery and back-in-time execution. The disclosed snapshot technique is designed to reduce the number of write operations to improve the performance on flash-based storage systems. The disclosed snapshot technique can guarantee data recovery no matter which of the production site or the backup site fails. The disclosed snapshot technique can also reduce the storage space requirement for snapshots by exploiting content locality. Furthermore, the disclosed snapshot technique can be implemented using hardware, software, firmware, or any combination of them. In case of hardware implementation, only minor hardware modifications are needed.