Storage Controller Write-Back Cache Using Host Persistent Memory
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Solution Overview
Problem
Storage controllers in Information Handling Systems (IHSs) are often limited to write-through caching in scenarios like RAID operations or when they have limited internal cache memory, which results in significant latency and restricts their ability to use write-back caching, even when it could improve performance.
Innovation Solution
Implementing a system where the storage controller can switch to write-back caching by requesting and utilizing host IHS memory, specifically persistent memory, to store write data, allowing confirmation of storage upon allocation in the host memory rather than the storage devices, thereby enabling write-back caching even in scenarios requiring write-through caching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If write-back caching is implemented in storage controller, then write operation latency is reduced and performance is improved, but the storage controller requires extensive internal cache memory and backup power systems which increases device complexity
Solution Approach 1:
The patent extracts the cache memory function from the storage controller and relocates it to the host system's persistent memory resources. The storage controller requests and utilizes host memory allocations for write-back caching operations, thereby eliminating the need for extensive internal cache memory and backup power systems in the storage controller while still achieving reduced write latency.
Solution Approach 2:
The patent enables host system memory to serve dual purposes: its original system functions and write-back caching for the storage controller. By allowing host persistent memory to be allocated and shared for storage controller caching operations, the same memory resources perform multiple functions, reducing the need for dedicated cache memory in the storage controller.
2Reliability
If write-through caching is used in storage controller, then data integrity is guaranteed, but write operation latency increases significantly
Solution Approach 1:
The patent implements dynamic write policy selection, allowing the storage controller to switch between write-through and write-back caching modes based on operational requirements. The controller can dynamically allocate host memory for write-back operations when performance is prioritized, and fall back to write-through mode when data integrity is the primary concern, providing flexible adaptation to different operational contexts.
Solution Approach 2:
The patent introduces host persistent memory as an intermediary layer between the storage controller and the storage devices. This intermediary enables write-back caching by providing a buffer that maintains data integrity through persistence capabilities, allowing the storage controller to acknowledge writes faster while maintaining reliability through the intermediary's persistent storage properties.
3Device complexity
If storage controller has limited internal cache memory, then device complexity is reduced, but the ability to implement write-back caching is restricted
Solution Approach 1:
The patent extends the caching resource dimension from local storage controller memory to host system memory resources. By operating in this additional dimensional space of host persistent memory, the storage controller gains access to significantly larger cache capacities without increasing its own internal complexity, enabling write-back caching capabilities that were previously unavailable to controllers with limited internal memory.
Data Source
AI summary
Systems and methods provide a storage controller with write-back caching capabilities that may be used during scenarios where the storage controller is required to provide write-through caching, and thus unable to utilize internal cache memory for write-back caching. The storage controller utilizes an allocation of persistent memory that is made available by the host IHS (Information Handling System), to which the storage controller is coupled. In scenarios where the storage controller is required to provide write-through caching, the storage controller may be configured to route received write data to the allocated host memory. In this manner, the data integrity provided by write-through operations is maintained, while also providing the host IHS with the speed of write-back operations. When ready to store the write data, the storage controller may request the flushing of write data from the allocated host memory.