Shadow Copy Volume Data Sharing via Differential Access
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Solution Overview
Problem
In computer systems, a server can become a bottleneck when accessing data from a storage subsystem due to high bandwidth requirements and concurrent requests from multiple clients, leading to reduced responsiveness.
Innovation Solution
Implementing a shadow copy mechanism where an active server creates a read-only shadow copy of a volume that can be accessed by passive servers, allowing them to read data from a differential area if changes have occurred, or directly from the original volume if not, thereby reducing the load on the active server.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single server mounts and accesses data from a storage subsystem, then the server can utilize the full bandwidth of the storage subsystem, but the server becomes a bottleneck due to high bandwidth requirements and concurrent requests from multiple clients
Solution Approach 1:
The system segments the server roles into active servers and passive servers. Active servers handle data writing and shadow copy creation, while passive servers handle data reading. This segmentation distributes the workload and prevents any single server from becoming a bottleneck, resolving the contradiction between maintaining high throughput and preserving server responsiveness.
Solution Approach 2:
The invention creates shadow copies of volumes that can be accessed by multiple passive servers simultaneously. Instead of having multiple servers access the same volume directly (which would create bottlenecks), the system creates copies that can be served concurrently, maintaining full bandwidth utilization while improving server responsiveness and client service quality.
2Ease of operation
If multiple servers access the same volume simultaneously, then server responsiveness improves and bottlenecks are reduced, but data consistency and access conflicts increase
Solution Approach 1:
The system performs preliminary actions by creating shadow copies before allowing passive servers to access data. These shadow copies are prepared in advance with the correct data state, ensuring that passive servers read consistent data without causing conflicts with active servers. This preliminary action maintains data consistency while enabling multiple servers to operate simultaneously.
Solution Approach 2:
Shadow copies act as intermediaries between active servers and passive servers. The active server writes to the original volume and updates shadow copies, while passive servers read from shadow copies. This intermediary mechanism prevents direct access conflicts and maintains data consistency across multiple servers.
3Productivity
If shadow copies are used to enable multiple servers to read data, then the load on the active server is reduced, but the complexity of managing differential areas and consistency checks increases
Solution Approach 1:
The system dynamically manages shadow copies by tracking which extents have been written to the differential area and adjusting read operations accordingly. Passive servers perform consistency checks only when necessary (when extents exist in the differential area), making the complexity adaptive rather than static. This dynamic approach improves data sharing efficiency while managing complexity through intelligent conditional checks.
Data Source
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AI summary
Aspects of the subject matter described herein relate to sharing volume data via shadow copies. In aspects, an active computer creates a shadow copy of a volume. The shadow copy is exposed to one or more passive computers that may read but not write to the volume. A passive computer may obtain data from the shadow copy by determining whether the data has been written to a differential area and, if so, reading it from the differential area. If the data has not been written to the differential area, the passive computer may obtain it by first reading it from the volume, then re-determining whether it has been written to the differential area, and if so, reading the data from the differential area. Otherwise, the data read from the volume corresponds to the data needed for the shadow copy.