Memory Controller Pseudo-Random Slot Indexing for SSD L2P Management
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Solution Overview
Problem
Solid-state drives (SSDs) face challenges in reducing the size of dynamic random access memory (DRAM) while maintaining low write amplification and avoiding coarse granularity access, which leads to increased latency and throughput degradation due to random workloads and cache misses.
Innovation Solution
A memory system that uses a table with entries associated with logical block addresses, where a memory controller executes pseudo-random functions to generate slot indexes for writing and reading data across multiple memory devices, allowing for efficient data management and reduced DRAM size without increasing write amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the size of DRAM is reduced by storing most of the L2P table in non-volatile memory, then DRAM size is reduced, but write amplification increases and latency increases due to random workloads causing cache misses
Solution Approach 1:
The L2P table is segmented into multiple slots distributed across different memory devices, channels, and ways. Each slot contains a portion of the L2P entries, allowing the system to divide the large L2P table into manageable segments that can be cached more efficiently in DRAM while maintaining fast access paths through the parallel memory structure
Solution Approach 2:
The patent introduces a new dimensional organization by distributing L2P entries across multiple dimensions: slots within memory devices, memory devices within channels, and channels within the memory controller. This multi-dimensional distribution allows parallel access paths that reduce cache misses and latency while maintaining reduced DRAM size
2Volume of stationary object
If random workloads are handled with a reduced DRAM L2P table, then DRAM size is reduced, but cache misses increase causing more frequent reads from non-volatile memory
Solution Approach 1:
The system pre-positions L2P table segments in appropriate memory slots and maintains cache warm by anticipating random workload patterns. The multi-slot structure allows proactive loading of L2P entries into DRAM cache before they are needed, reducing cache misses and maintaining throughput during random workloads
Solution Approach 2:
The patent changes the organizational parameters of the L2P table from a single monolithic structure to a distributed multi-slot structure with different replication factors and distribution patterns. This parameter change enables the system to optimize for both DRAM size reduction and throughput maintenance by adjusting how L2P entries are distributed and cached across the memory hierarchy
3Volume of stationary object
If a smaller DRAM is used for L2P table storage, then cost is reduced, but write amplification increases when maintaining the L2P table
Solution Approach 1:
The L2P table is segmented into multiple slots that can be updated independently. When L2P entries need to be updated, the system can perform incremental updates to specific slots rather than rewriting the entire L2P table, significantly reducing write amplification while maintaining a compact DRAM footprint
Solution Approach 2:
Different slots in the distributed L2P table structure can have different update frequencies and persistence requirements. The system applies local quality by optimizing update strategies for each slot based on its specific access patterns and importance, reducing overall write amplification while maintaining data integrity
Data Source
AI summary
A memory system includes a table storing a plurality of entries, where each entry is associated with a different logical block address (LBA), a plurality of memory devices, channels, and ways, where each memory device is connected to one of the channels ways and to one of the ways, and a memory controller configured to receive an LBA and data from a host, execute a plurality of pseudo-random functions on the received LBA to generate a plurality of slot indexes, select one of the slot indexes, write the data to one of the memory devices identified by the selected one slot index, and update a corresponding one of the entries to include the selected one slot index.