Virtualized Storage Appliance for Non-Disruptive Data Migration
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Solution Overview
Problem
Existing data migration techniques between different data storage systems are often disruptive to applications, causing interruptions in service as they require direct access to physical storage devices, which can lead to downtime and complications in maintaining continuous operation.
Innovation Solution
The introduction of a storage appliance that provides virtualized storage, allowing for non-disruptive insertion between hosts and data storage systems by presenting logical devices with the same data store signature, enabling seamless migration of virtual machines and applications while maintaining data integrity and availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct access to physical storage devices is used for data migration, then data migration can be performed, but service interruptions and application downtime occur
Solution Approach 1:
A storage appliance is introduced as an intermediary device between hosts and data storage systems. The appliance receives I/O requests from hosts and forwards them to the appropriate data storage system, enabling seamless data migration without requiring hosts to directly access physical storage devices. This mediator approach allows migration to occur transparently, maintaining continuous service availability.
Solution Approach 2:
The system is segmented into distinct functional components: hosts, storage appliance (with virtualization layer), and data storage systems. This segmentation allows the virtualization layer to independently manage data migration paths, enabling migration operations to proceed without interrupting host applications. The logical device presentation separates the migration complexity from the application layer.
2Reliability
If storage appliance with virtualized storage is inserted, then non-disruptive data migration is enabled, but device complexity increases
Solution Approach 1:
The storage appliance is designed as a universal platform that can interface with multiple different data storage systems from various vendors and present unified logical devices to multiple hosts. This multi-functionality consolidates what would otherwise require multiple specialized components, managing complexity through standardization rather than proliferation of specialized devices.
Solution Approach 2:
The storage appliance creates virtual copies of physical storage devices as logical devices. These virtualized logical devices present an abstracted interface that simplifies host access while the appliance handles the complexity of mapping to underlying physical storage. The copying approach allows migration without requiring hosts to be aware of or directly access complex physical storage architectures.
3Adaptability or versatility
If logical device identifier is changed during migration, then storage flexibility is improved, but data access continuity is disrupted
Solution Approach 1:
The storage appliance maintains continuous I/O operations during migration by intercepting requests from hosts and dynamically routing them to appropriate physical storage devices. The virtualization layer ensures that useful action (data access) continues uninterrupted while the underlying storage configuration changes. Hosts continue to access logical devices with consistent identifiers while migration occurs in the background.
Solution Approach 2:
The appliance acts as an intermediary that decouples the logical device identifier from the physical storage device identifier. This allows the logical device ID to remain constant for continuity while the physical mapping changes during migration. The mediator translates between stable logical identifiers and dynamic physical storage locations, enabling reconfiguration without disrupting data access.
Data Source
AI summary
Non-disruptive insertion of a storage appliance provides virtualized storage. A first logical device of a data storage system is exposed to a first host and a second host. A data store of the first logical device is uniquely identified using a signature. After inserting the storage appliance between the first host and the data storage system, the first logical device is presented, through the storage appliance, to the first host as a second logical device. After inserting the storage appliance between the second host and the data storage system, the first logical device is presented, through the storage appliance, to the second host as the second logical device. The first and second hosts identify the second logical device and the first logical device as the same logical device using the signature. The data store may be a virtual machine file system data store used by virtual machines on the hosts.