Dual Storage Virtualization Controllers Active-Active Data Access
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Solution Overview
Problem
Existing data storage systems with dual storage virtualization controllers face challenges in ensuring high reliability and performance due to issues like data loss during controller failures and inefficient access methods, which complicate data replication and access across redundant pairs.
Innovation Solution
A method is introduced where the second storage virtualization controller inquires about address information from the first controller, assigns corresponding data storage addresses, and multicasts written data to both controllers, ensuring simultaneous writing and reducing the risk of data loss by maintaining data integrity across the redundant pair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second SVC denies the access request when the host intends to access LDs managed by the first SVC, then the host must re-issue the access request to the first SVC, but this worsens the access performance of the host entity
Solution Approach 1:
The second SVC proactively queries the first SVC for address information before the host issues the access request. By obtaining the address mapping in advance, the second SVC can directly forward the host's access request to the correct location without denying it, thus maintaining both reliability and performance.
2Reliability
If the first SVC replicates written data to the second SVC after receiving the data, then data integrity is maintained, but this increases the time for write operation completion and reduces system performance
Solution Approach 1:
The system performs preliminary actions by having the second SVC query address information and prepare storage locations before the actual write operation. This allows the write data to be simultaneously written to both SVCs in parallel, rather than sequentially replicating after the first SVC completes its write.
Solution Approach 2:
The write operations to the first SVC and second SVC are merged into a single simultaneous operation. Both controllers receive and write the write data at the same time, eliminating the sequential replication delay while maintaining data integrity across both controllers.
3Reliability
If the second SVC writes data to its own memory and the first memory simultaneously, then data loss risk is reduced during controller failures, but this requires complex address management and inter-controller communication
Solution Approach 1:
The first SVC acts as an intermediary that responds to queries from the second SVC with address information. This mediator role simplifies the address management for the second SVC, which can directly use the provided addresses without implementing its own complex address translation logic.
Solution Approach 2:
The system implements a feedback mechanism where the second SVC queries the first SVC for address information, and the first SVC provides the necessary address mapping. This feedback loop enables coordinated simultaneous writes with proper address management, reducing complexity compared to independent address management by both controllers.
Data Source
AI summary
In a storage system architecture having two storage virtualization controllers (SVCs) that operate in an active-active mode, the corresponding relationships between storage addresses in the two buffers of the two SVCs are pre-determined. When a non-owner SVC that does not have an ownership over a logical disk (LD), receives an I/O request from a host, the non-owner SVC will inquire of the other SVC having the ownership, about associated address information, and then the non-owner SVC that does not have the ownership over the LD will perform, according to the associated address information, the I/O request from the host. Therefore, data synchronization operation for mutually backing up data between the two SVCs can be fast achieved. Also, it allows the host to issue a data access request to any one of the SVCs, thus improving performance of the storage system.