RAID Controller Optimizing Rebuild via Unmapped LBA Detection

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Solution Overview

Problem

RAID array rebuild operations are time-consuming due to the need to read data from multiple SSDs, especially when many logical block addresses (LBAs) are mapped, which limits the performance and efficiency of the rebuild process in RAID systems.

Innovation Solution

A method to determine data corresponding to a stripe in a RAID array by identifying unmapped LBAs, allowing the RAID array controller to skip reading data from SSDs that have unmapped LBAs during rebuild, resync, or exposed mode read operations, thereby reducing the number of SSD reads and improving bandwidth utilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the RAID array controller reads data from multiple SSDs during rebuild operations, then data integrity is ensured, but the rebuild time increases significantly

Engineering Contradiction:

Improvedata integrityVSAvoidrebuild time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts and identifies unmapped LBAs separately from the rebuild process. By detecting which LBAs are unmapped beforehand, the system can exclude those regions from the read-intensive rebuild operation, thereby reducing overall rebuild time while maintaining data integrity for mapped regions

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary identification of unmapped LBAs before initiating the rebuild operation. This preliminary action allows the system to pre-calculate which SSD regions can be skipped during rebuild, optimizing the subsequent data recovery process without compromising reliability

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the RAID array controller reads data from all SSDs during rebuild operations, then complete data recovery is achieved, but bandwidth utilization decreases

Engineering Contradiction:

Improvedata recovery completenessVSAvoidbandwidth utilization

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent extracts information about unmapped LBAs and uses this information to exclude unnecessary SSD reads from the rebuild process. This selective approach maintains complete data recovery for mapped regions while significantly reducing bandwidth consumption by skipping unmapped regions

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of performing a complete read of all SSD data, the patent applies partial action by reading only the necessary mapped regions. This partial rebuild approach achieves sufficient data recovery without the excessive bandwidth consumption of a full array read

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10628054B2Raid array systems and operations using mapping information

Publication Date: 2020.04.21 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

An apparatus may include a redundant array of independent disks (RAID) array including a plurality of solid state drives (SSDs). The apparatus may further include a RAID array controller coupled to the plurality of SSDs. The RAID array controller may be configured to determine whether one or more logical block addresses (LBAs) of a stripe of the RAID array are unmapped. The one or more LBAs may be associated with one or more SSDs of the plurality of SSDs. The RAID array controller may be configured to determine data corresponding to the stripe based on the determination of whether the one or more LBAs are unmapped. RAID operations (such has Rebuild, Exposed Mode Read, and/or Parity Resync operations) may be optimized based on the knowledge of which LBAs are mapped and unmapped.