Storage Array Resync Using In-Flight Write Tracking

Solution Overview

Problem

Storage systems relying on snapshots for resyncing out-of-sync storage arrays face inefficiencies due to unnecessary data re-sending and lack of flexibility in handling array unavailability, leading to resource wastage and prolonged resync times.

Innovation Solution

Implementing a system that tracks write requests and acknowledgments using sequence identifiers and acknowledgement indicators, allowing for efficient resyncing without relying on last common snapshots, and enabling flexible reconfiguration of storage arrays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If storage systems use snapshots for resyncing out-of-sync storage arrays, then data consistency can be restored, but resource usage increases and resync time is prolonged due to unnecessary data re-sending

Engineering Contradiction:

Improvedata consistencyVSAvoidresource usage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system performs preliminary tracking of write requests and acknowledgments before a failure occurs. By maintaining records of which writes have been acknowledged during normal operation, the system prepares advance information that eliminates the need for comprehensive data re-sending during resync, thus reducing resource usage while maintaining data consistency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention extracts only the necessary information (acknowledged write requests) from the complete data set for resync purposes. Instead of re-sending all data or using full snapshots, the system isolates and transmits only the specific write acknowledgments that are needed to restore consistency, significantly reducing resource consumption

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If storage systems use snapshots for resyncing, then data consistency can be restored, but resync time is prolonged due to unnecessary data re-sending

Engineering Contradiction:

Improvedata consistencyVSAvoidresync time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary tracking of write requests and acknowledgments before a failure occurs. By maintaining records of which writes have been acknowledged during normal operation, the system prepares advance information that eliminates the need for comprehensive data re-sending during resync, thus reducing resync time while maintaining data consistency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention extracts only the necessary information (acknowledged write requests) from the complete data set for resync purposes. Instead of re-sending all data or using full snapshots, the system isolates and transmits only the specific write acknowledgments that are needed to restore consistency, significantly reducing resync time

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If storage systems rely on last common snapshots for resyncing, then resync can be performed, but flexibility in handling array unavailability is reduced

Engineering Contradiction:

Improveresync capabilityVSAvoidflexibility in handling array unavailability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system dynamically adapts its resync behavior based on the specific failure scenario. By tracking write acknowledgments in real-time, the system can determine the exact state of data consistency and adjust the resync process accordingly, providing flexibility to handle various unavailability scenarios including partial failures, network issues, and different failure timings

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention implements feedback mechanisms where write acknowledgments are tracked and used to inform subsequent resync decisions. This feedback loop allows the system to understand the actual state of data replication and adjust its resync strategy dynamically, enhancing adaptability to different failure conditions while maintaining reliable resync capability

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10732860B2Recordation of an indicator representing a group of acknowledgements of data write requests

Publication Date: 2020.08.04 HEWLETT PACKARD ENTERPRISE DEV LP

AI summary

Examples described herein include receiving a first data write request from a host computing device, assigning a first identification to the first data write request, recording the first identification in in-flight data, transmitting the first data write request to a second storage array, receiving a first acknowledgement of the first data write request from the second storage array, and recording an indicator representing a group of acknowledgements. In some examples, the group of acknowledgements comprises the first acknowledgment.