Asymmetric Storage Controller Access for Fast Failover
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Solution Overview
Problem
Conventional storage environments face prolonged unavailability due to time-consuming takeover procedures when a storage controller fails, as non-owner controllers lack immediate access to updated data, leading to inefficient fail-over recovery.
Innovation Solution
Configuring a storage environment with a symmetric frontend and asymmetric backend, where non-owner storage controllers can execute write commands but not commit them, and instead notify the owner controller for synchronization, allowing for efficient data synchronization and reduced downtime during failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional storage environment with independent storage controllers is used, then each controller has clear ownership and access control, but takeover procedure becomes time-consuming when a controller fails
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing data between owner and non-owner storage controllers before failure occurs. Non-owner controllers maintain updated copies of write buffers and log memories, so when a takeover is needed, the non-owner controller already has current data and can immediately assume ownership without time-consuming image restoration procedures.
2Loss of time
If non-owner storage controllers are granted full access to all storage devices, then failover becomes faster, but data consistency and access control become problematic
Solution Approach 1:
The patent applies local quality by giving different access permissions to different storage devices based on ownership. Non-owner controllers can access and synchronize data from specific storage devices associated with the owner controller, but cannot arbitrarily modify all storage devices in the system. This selective access approach enables faster failover while maintaining data consistency through controlled synchronization paths.
Solution Approach 2:
The patent implements feedback mechanisms where non-owner controllers notify owner controllers of data modifications, and owner controllers provide synchronization updates. This feedback loop ensures data consistency is maintained during normal operation and during failover transitions, allowing non-owner controllers to have sufficient data for immediate takeover without compromising overall system consistency.
3Reliability
If image restoration is performed during takeover, then data consistency is restored, but service interruption is extended
Solution Approach 1:
The patent eliminates the need for image restoration during takeover by pre-synchronizing data to non-owner controllers. Since non-owner controllers already maintain current copies of write buffers and log memories, they can immediately assume ownership and continue servicing I/O requests without requiring time-consuming image restoration procedures, thus maintaining both data consistency and service availability.
Data Source
AI summary
One or more techniques and/or systems are provided for configuring a storage environment. In particular, the storage environment may be configured with a symmetric frontend and an asymmetric backend. That is, an owner storage controller may be granted read/write access to a storage device owned by the owner storage controller, while a non-owner storage controller may be granted merely read access. In this way, the owner storage controller may execute, log, and/or commit a write command to the storage device, while the non-owner storage controller may merely execute, but not log and/or commit, a write command. Write buffers, log memories, and/or file system metadata may be synchronized between the owner storage controller and the non-owner storage controller, such that the non-owner storage controller may efficiently take ownership of the storage device in response to a failure of the owner storage controller.