Multi-Layer Cache Eviction for Data Storage Access Speed
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Solution Overview
Problem
The existing data storage systems face challenges in optimizing data access speed due to the long time required for host devices to read data from storage devices, necessitating a caching policy between host devices and storage devices to improve operation efficiency.
Innovation Solution
A data storage apparatus comprising a first memory device, a second memory device, and a storage device, with a controller that manages data by storing write data in the first memory device, copying it to the second memory device, and evicting eviction target data to the storage device and first memory device, thereby reducing access frequency to the slower storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If data is stored directly in the storage device, then storage capacity is sufficient, but data access time is long
Solution Approach 1:
The storage system is segmented into multiple memory devices with different speeds (first memory device, second memory device, and storage device), creating a hierarchical structure where faster memory devices handle frequent access while slower devices provide bulk storage capacity
Solution Approach 2:
The patent introduces a multi-dimensional memory hierarchy by adding both speed dimension (fast to slow memory devices) and capacity dimension (small to large storage), allowing data to be positioned optimally across different layers based on access frequency
2Reliability
If a single memory device is used, then device complexity is low, but cache hit probability is insufficient
Solution Approach 1:
Multiple memory devices are nested in a hierarchical structure where the first memory device (fastest) is nested within the second memory device (slower), which is in turn nested within the storage device (slowest), creating concentric layers of caching
Solution Approach 2:
The second memory device acts as an intermediary between the first memory device and the storage device, buffering data transfers and managing evictions to reduce direct access to the slowest storage device
3Speed
If fast memory device is used for all data, then access speed is high, but storage capacity is insufficient
Solution Approach 1:
Different regions of the storage hierarchy are assigned different speed characteristics - the first memory device provides high-speed access for frequently accessed data, while the storage device provides large-capacity storage for less frequently accessed data
4Productivity
If eviction target data is only stored in storage device, then storage device access frequency increases, but second memory device space is freed
Solution Approach 1:
When evicting data from the second memory device, the system proactively copies eviction target data to the first memory device before it is needed, ensuring that frequently accessed data remains in fast memory and reducing subsequent access to the storage device
Data Source
AI summary
A data storage apparatus may include a first memory device comprising a first area in which write data from a host device are stored and a second area, a second memory device into which the write data stored in the first memory device are copied, a storage device, and a controller. The controller is configured to control data input/output for the first memory device, the second memory device and the storage device, wherein the controller comprises a cache manager configured to evict eviction target data from the second memory device by: storing the eviction target data into the storage device, and storing the eviction target data into the second area of the first memory device.