Flash Memory Cache Switching Between SLC and XLC Modes
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Solution Overview
Problem
Existing memory devices struggle to optimize the dynamic management of cache memory functions, leading to inefficiencies in performance and capacity due to varying usage conditions and performance characteristics, which hinder the full exploitation of different capabilities in flash memory devices.
Innovation Solution
A memory device with dynamic cache management that dynamically adjusts the operating mode of memory blocks based on the amount of valid data and write amplification, using single-level cells (SLCs) as cache for faster write performance and managing cache memory by recognizing work patterns to improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory devices use extra-level cells (XLCs) for higher storage capacity and density, then storage capacity is improved, but write performance deteriorates due to slower operating speeds
Solution Approach 1:
The memory device divides its storage into multiple blocks with different operating modes (SLC mode for high-speed writing and XLC mode for high-capacity storage). This segmentation allows the system to allocate specific blocks for cache functions and others for bulk storage, resolving the contradiction between speed and capacity by spatial separation of functions.
Solution Approach 2:
The memory device dynamically switches between SLC and XLC operating modes based on workload conditions. During idle periods or when write buffer needs expansion, blocks are dynamically reconfigured from XLC mode to SLC mode to provide faster write performance, while under normal conditions they operate in XLC mode for maximum capacity.
2Speed
If memory devices allocate more blocks for cache functions to improve write performance, then write performance is improved, but storage capacity is reduced
Solution Approach 1:
The cache block allocation is dynamic rather than static. The memory device monitors workload conditions and automatically adjusts the number of blocks dedicated to cache functions. During periods of low write activity, cache blocks are reduced to maximize storage capacity, while during high write activity periods, more blocks are allocated to cache to maintain write performance.
Solution Approach 2:
The operating mode parameter of memory blocks is changed dynamically between SLC and XLC modes based on system needs. This parameter change allows the same physical blocks to serve different functions (cache or storage) at different times, enabling the system to optimize both write performance and storage capacity without permanent allocation.
3Productivity
If memory devices perform garbage collection to manage cache blocks, then cache efficiency is improved, but write amplification and processing time increase
Solution Approach 1:
Garbage collection is performed periodically during idle periods rather than continuously or on-demand. The memory device schedules garbage collection operations to execute during low-activity periods, allowing cache blocks to be cleaned and reused without impacting write performance during active periods. This periodic approach balances cache efficiency with minimal processing time loss.
Data Source
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AI summary
A memory system includes a memory array having a plurality of memory cells; and a controller coupled to the memory array, the controller configured to: select a garbage collection (GC) source block storing valid data, calculate a valid data measure for the GC source block for representing an amount of the valid data within the GC source block, and designate a storage mode for an available memory block based on the valid data measure, wherein the storage mode is for controlling a number of bits stored per each of the memory cells for subsequent or upcoming data writes.