SSD Cache Management via Preloading and Write Merging
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Solution Overview
Problem
Standard cache replacement policies in SSDs lead to cache pollution, especially with many small write requests, which negatively impacts SSD performance and endurance.
Innovation Solution
The SSD controller optimizes cache management by preloading data offline in read-only cache mode and minimizing write requests to the NAND flash memory by writing at a small granularity and evicting data in a way that reduces backend writes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard cache replacement policies are used in SSD, then cache management is simple, but cache pollution occurs and performance deteriorates
Solution Approach 1:
The patent applies preliminary action by preloading data into the cache before it is actually needed. The SSD controller proactively loads data from NAND flash into the cache buffer in advance, so that when read requests arrive, the data is already available in the cache, avoiding cache pollution from reactive replacement policies and improving read performance.
2Ease of operation
If standard cache replacement policies are used in SSD, then cache management is simple, but cache hit rate decreases
Solution Approach 1:
The patent applies preliminary action by preloading data into the cache before it is actually needed. The SSD controller proactively loads data from NAND flash into the cache buffer in advance, so that when read requests arrive, the data is already available in the cache, avoiding cache pollution from reactive replacement policies and improving read performance.
3Speed
If write requests are processed immediately in SSD, then write speed is fast, but number of backend writes increases and endurance decreases
Solution Approach 1:
The patent applies merging by combining multiple small write requests into larger write operations. The SSD controller buffers incoming write requests and merges them into larger write units before writing to NAND flash, reducing the total number of backend writes while maintaining fast write performance, thereby extending SSD endurance.
Solution Approach 2:
The patent applies preliminary action by preloading data into the cache before it is actually needed. The SSD controller proactively loads data from NAND flash into the cache buffer in advance, so that when read requests arrive, the data is already available in the cache, avoiding cache pollution from reactive replacement policies and improving read performance.
4Ease of operation
If write requests are processed immediately in SSD, then write operations are simple, but number of NAND flash writes increases
Solution Approach 1:
The patent applies merging by combining multiple small write requests into larger write operations. The SSD controller buffers incoming write requests and merges them into larger write units before writing to NAND flash, reducing the total number of backend writes while maintaining fast write performance, thereby extending SSD endurance.
Data Source
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AI summary
Methods and memory devices are provided. A request is received from a host device at a memory device in a first state. In case that the request is a read request, first data is read from a cache of the memory device based on the read request, and the first data is output to the host device. The cache is loaded with data with the memory device in a second state. In case that the request is a write request, a block of the cache is modified to remove cache data, the cache data and corresponding data from the cache are written to a flash memory of the memory device, and second data is written to the block of the cache based on the received write request.