Non-disruptive Logical Storage Migration in Linux Multi-pathing
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Solution Overview
Problem
Conventional approaches for migrating logical storage devices, especially in a Linux native multi-pathing environment, are disruptive and require manual intervention, making them inefficient and costly.
Innovation Solution
Implementing a multi-path layer with an MPIO driver that suspends and resumes IO operations, creates a proxy device, sets up mirroring, inserts a request splitter, and redirects paths to achieve non-disruptive migration of logical storage devices between storage systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional migration approaches are used, then migration can be completed, but the process is disruptive and requires manual intervention
Solution Approach 1:
The migration system performs self-service through automated discovery of storage paths, dynamic creation of proxy devices, automatic request splitting between old and new storage devices, and automated path redirection. The MPIO driver and device mapper automatically manage the migration process without requiring manual configuration or intervention, enabling the system to service itself during the migration operation.
2Productivity
If storage device migration is performed, then storage optimization is achieved, but IO operations are disrupted
Solution Approach 1:
A proxy device is introduced as an intermediary between the host application and the storage devices during migration. The proxy device receives IO requests and automatically splits them into two paths: one to the old storage device and one to the new storage device. This intermediary mechanism allows seamless data migration while maintaining continuous IO operations without disruption to the application.
Solution Approach 2:
The system performs preliminary actions by pre-creating the proxy device and establishing the request splitting mechanism before actual data migration begins. The migration infrastructure is prepared in advance, with paths to both old and new storage devices configured, ensuring that IO operations can continue uninterrupted while the migration proceeds in the background.
3Loss of time
If manual migration procedures are used, then migration can be completed, but time and resources are consumed
Solution Approach 1:
The migration system automatically discovers storage paths, identifies appropriate source and target devices, creates proxy devices, configures request splitting, and manages path redirection without human intervention. This self-service automation eliminates the time-consuming manual configuration steps and accelerates the overall migration process while maintaining system reliability.
Data Source
AI summary
A first logical storage device associated with a first multi-path device is migrated to a second logical storage device associated with a second multi-path device. The migrating illustratively comprises suspending the first multi-path device, creating a proxy device for the first multi-path device, implementing a mirror device to provide a mirroring arrangement between the proxy device and the second multi-path device, inserting a request splitter between the first multi-path device and the mirror device, redirecting output of the first multi-path device to the request splitter, and resuming the first multi-path device. Responsive to synchronization of the proxy device and the second multi-path device via the mirroring arrangement, the migrating further comprises suspending the first multi-path device, removing the request splitter, the mirror device and the proxy device, redirecting output of the first multi-path device to the second logical storage device, and resuming the first multi-path device.