Storage Apparatus Log Buffer for Power Failure Data Recovery

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Solution Overview

Problem

Conventional storage apparatuses, both dedicated hardware and general-purpose servers, face challenges in protecting memory data during power failures, with dedicated hardware lacking battery backup and general-purpose servers incurring additional costs for external battery solutions like UPS.

Innovation Solution

A storage apparatus comprising a memory unit with a cache area, management area, and log buffer, along with a non-volatile storage device for log data, which generates and collectively writes log data to a log chunk for data protection, ensuring data integrity even during power failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dedicated hardware storage apparatus is used with internal battery for memory data protection, then data reliability during power failure is improved, but device complexity and cost increase

Engineering Contradiction:

Improvememory data protectionVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the battery backup function from the storage apparatus and replaces it with a software-based logging mechanism. The log buffer and log chunk structure separate critical data protection from the physical hardware, allowing data recovery through log replay without requiring battery-powered memory retention.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/electrical battery backup system with a software-based logging and recovery system. Instead of using power to maintain memory state, the system uses sequential logging of data changes and management information, which can be replayed after power failure to restore data integrity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If general-purpose server is used without internal battery, then device complexity is reduced, but memory data protection during power failure deteriorates

Engineering Contradiction:

Improvedevice complexityVSAvoidmemory data protection

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements preliminary action by continuously maintaining a log buffer with data change information and management information before power failure occurs. This log buffer is periodically flushed to non-volatile storage as log chunks, ensuring that even if power is lost, the data can be recovered by replaying the logged changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary logging system between the volatile memory and the external storage. The log buffer acts as a mediator that captures data changes and management information, allowing the system to recover from power failure by replaying these logs without requiring battery backup in the memory itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If external battery such as UPS is prepared for power failure coping, then memory data protection is improved, but cost increases

Engineering Contradiction:

Improvememory data protectionVSAvoidcost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent replaces expensive battery backup infrastructure with a software-based logging mechanism that uses existing non-volatile storage resources. The log chunks are written to regular storage media without requiring specialized battery-powered components, significantly reducing hardware costs while maintaining data protection capabilities.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Reliability

If log data is written individually to non-volatile storage, then data protection is improved, but processing time increases

Engineering Contradiction:

Improvedata protectionVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent merges multiple log writes into collective operations. The log buffer accumulates data changes and management information, then flushes them to non-volatile storage as complete log chunks. This batching approach reduces the number of individual I/O operations while ensuring data protection through the logging mechanism.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements periodic action by flushing the log buffer to non-volatile storage at regular intervals or when certain conditions are met. This periodic flushing balances data protection requirements with performance considerations, avoiding continuous writing while ensuring logs are persisted before potential power failure.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS10776044B2Storage apparatus, data management method, and non-transitory computer readable medium

Publication Date: 2020.09.15 HITACHI VANTARA LTD

AI summary

A server including a memory unit, a processor unit, and a storage device, wherein the memory unit has: a CM; an SM which stores management information; and a log buffer for storing log data indicating contents of change to the CM and the SM. The storage device has a log chunk for storing the log data, and the processor unit is configured to: store target data corresponding to an I/O request in the CM; generate log data of contents of change with respect to the CM and the SM, and to store the pieces of the generated log data in the log buffer; write a plurality of pieces of log data stored in the log buffer into the log chunk; and transmit, after all of the pieces of log data corresponding to the I/O request are written into the log chunk, a response of good to a request source.