Storage Controller Cache Coordination Overhead
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Solution Overview
Problem
In storage systems using multiple cache memories across controllers, data often needs to be transferred between controllers, causing overhead when the receiving controller is different from the cache controller, leading to inefficient data retrieval.
Innovation Solution
Implement a system where the receiving controller determines if it is associated with the read source storage area and, if not, transfers the read request to the associated controller while reading and caching the data locally, thereby avoiding unnecessary data transfers between controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is cached in CM of cache controller and transferred to CM of receiving controller when they are different, then the read request can be processed through cache, but the data needs to pass memory multiple times causing large overhead
Solution Approach 1:
The patent merges the functions of cache controller and receiving controller by enabling the receiving controller to directly read data from storage device and cache it in its own CM, eliminating the need for separate data transfer between controllers and reducing memory access overhead while maintaining cache hit functionality
2Reliability
If multiple controllers share cache management information through synchronized memory, then cache coordination is achieved, but system complexity increases
Solution Approach 1:
The patent extracts the complex synchronization mechanism from the system by having each controller independently manage its own CM and make local decisions about data caching and request handling, eliminating the need for continuous inter-controller synchronization while maintaining cache coordination through independent CM management
3Loss of time
If receiving controller transfers read request to associated controller, then data transfer between controllers is avoided, but the receiving controller must read and cache data locally increasing its workload
Solution Approach 1:
The patent applies self-service by enabling each receiving controller to independently read data from the storage device and cache it in its own CM without requiring assistance from other controllers, reducing inter-controller data transfer overhead while distributing the workload across multiple controllers
Data Source
AI summary
A receiving controller which receives a read request out of first and second storage controllers transfers the read request to an associated controller which is associated with a read source storage area out of the first and second storage controllers when the receiving controller is not the associated controller. It is however the receiving controller that reads the read-target data from a read source storage device, writes the read-target data to a cache memory of the receiving controller, and transmits the read-target data written in the cache memory of the receiving controller to a host apparatus.