Storage Controller Data Migration Without Host Disruption
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Solution Overview
Problem
Data migration between storage devices in a storage system requires operations that change host computer recognition, necessitating changes in host computer information and potentially closing applications.
Innovation Solution
A storage system with two controllers and storage devices that perform data migration while maintaining continuous host access by updating association information and releasing logical storage areas, allowing seamless transition without disrupting host computer operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data migration is performed from one storage device to another, then data can be moved between storage devices, but host computer information must be changed and applications may need to be closed
Solution Approach 1:
The system divides the storage management into two independent controllers: a first controller that manages the virtual volume and association information, and a second controller that performs data migration. This segmentation allows the host computer to continue accessing the virtual volume through the first controller while data is migrated by the second controller, eliminating the need to change host information or close applications.
Solution Approach 2:
The first controller acts as an intermediary between the host computer and the storage devices. It maintains the virtual volume and association information that maps virtual volumes to real volumes. During data migration, the first controller continues to respond to host requests, while the second controller handles the actual data transfer between storage devices, shielding the host from migration operations.
2Reliability
If data migration is performed, then data can be moved between storage devices, but information stored in host computer must be changed
Solution Approach 1:
The system separates the virtual volume management function (first controller) from the physical storage management function (second controller). The first controller maintains stable association information that the host computer uses, while the second controller handles physical data migration. This segmentation allows data migration without requiring changes to host computer information.
Solution Approach 2:
The first controller maintains a copy of the association information that maps virtual volumes to real volumes. During data migration, this association information is updated to reflect the new mapping, while the host computer continues to use the same virtual volume interface. The host is unaware of the physical changes because it interacts only with the virtual volume interface.
Data Source
AI summary
The access from a host computer to a storage system is continued before and after data migration in the storage system. A first controller allocates a first logical storage area to a specific virtual storage area, stores first association information indicating the specific virtual storage area and the first logical storage area, and sends the first association information to the host computer. The first controller and the second controller perform data migration from the first logical storage area to a second logical storage area. The first controller releases the first logical storage area from the specific virtual storage area and reflects the release in the first association information. The second controller allocates the second logical storage area to the specific virtual storage area, stores second association information indicating the specific virtual storage area and the second logical storage area, and sends the second association information to the host computer.