HA Storage Volume Migration with Exclusion Locks

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Solution Overview

Problem

In active-active-type HA storage systems, data migration while maintaining high availability and non-stoppage of host I/O access is challenging, leading to potential data corruption due to parallel writing to multiple volumes without simultaneous writing to all volumes.

Innovation Solution

Implementing an HA pair migration method that configures a new volume pair by copying data from a primary volume to a secondary volume, using exclusion locks to manage write and read operations, ensuring data uniformity and preventing corruption by prioritizing writes to the primary volume and subsequent parallel writes to secondary volumes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If data is written in parallel to PVOL, SVOL1 and SVOL2, then writing speed is improved, but data consistency deteriorates due to potential data corruption

Engineering Contradiction:

Improvewriting speedVSAvoiddata consistency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by requiring that write data be written to the PVOL first before being written to the SVOLs. This sequencing ensures that the primary volume has the latest data before secondary volumes receive it, preventing data corruption while still enabling parallel writing to multiple volumes for improved performance

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The PVOL serves as an intermediary between the host and the SVOLs in the write path. All write operations must first complete on the PVOL before propagating to SVOL1 and SVOL2, making the PVOL a mediator that ensures data consistency across the volume group while allowing parallel processing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If exclusion locks are used to ensure data consistency, then data integrity is improved, but I/O processing speed deteriorates

Engineering Contradiction:

Improvedata integrityVSAvoidI/O processing speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by acquiring the PVOL exclusion lock before writing to the PVOL, ensuring that the primary volume is exclusively accessed during critical write operations. This prevents data corruption while minimizing lock duration by only locking during the actual write operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies local quality by using exclusion locks selectively only on the PVOL during write operations, not on all volumes. This localized locking approach ensures data integrity where it's most critical (at the primary volume) while avoiding unnecessary locking overhead on secondary volumes that can be written to in parallel

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10860235B2Storage system having a plurality of storage apparatuses which migrate a first volume group to a second volume group

Publication Date: 2020.12.08 HITACHI VANTARA LTD

AI summary

The first to third storage apparatuses each comprise an SVOL1, SVOL2 and PVOL. Even when the write command designates any of the PVOL, SVOL1 and SVOL2, at least one of the first to third storage apparatuses writes write target data according to the write command to the PVOL and then writes the write target data in parallel to the SVOL1 and SVOL2. Even if a read command designates any of the PVOL, SVOL1 and SVOL2, at least one of the first to third storage apparatuses reads read target data according to the read command from the PVOL.