Die Access Order Variation for Multi-Die NAND
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Solution Overview
Problem
Solid state memory (SSM) systems with multiple die architectures face significant performance issues due to simultaneous data access collisions, leading to resource shortages, cascading delays, and poor quality of service, as multiple streams competing for access to shared NAND dies result in bursts of collisions that overwhelm available resources.
Innovation Solution
A die access order module (DAOM) within the storage controller assigns distinct die access orders to each stream, distributing the timing of data access collisions and preventing repeated collisions by varying the order in which dies are accessed, using modular multiplication or lookup tables to determine unique access sequences for each stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple streams access shared NAND dies simultaneously, then data throughput increases, but die collision frequency increases causing resource shortages and cascading delays
Solution Approach 1:
The patent implements dynamic die access order adjustment where the controller varies the access sequence of NAND dies based on stream identification. Each stream is assigned a different die access order, transforming the static access pattern into a dynamic one that adapts to multiple concurrent streams, thereby reducing simultaneous collisions while maintaining high throughput
Solution Approach 2:
The patent segments the die access operations by stream, dividing the concurrent access into separate ordered sequences. Each stream receives a dedicated access order, preventing the interleaving conflicts that occur with unified access patterns. This segmentation isolates collision sources and allows parallel execution with reduced interference
2Reliability
If die access order is varied per stream, then simultaneous die collisions are reduced, but controller complexity increases
Solution Approach 1:
The patent changes the parameter of die access order from a fixed sequence to a variable sequence based on stream ID. By modifying this single parameter dynamically, the system achieves collision reduction without fundamentally altering the controller architecture. The variation is implemented through simple reordering logic rather than complex additional circuitry
Solution Approach 2:
The controller generates its own varied access orders internally using stream identification information already available in the data path. This self-service approach eliminates the need for external arbitration or complex scheduling mechanisms, reducing overall system complexity while achieving the desired collision reduction
3Reliability
If more buffer capacity is added to handle collisions, then quality of service improves, but device cost and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-establishing different die access orders for different streams before collisions occur. This preventive measure eliminates the need for reactive buffer expansion to handle collision backlogs. By organizing access patterns in advance, the system avoids the resource exhaustion that would otherwise require additional buffering capacity
Data Source
AI summary
Systems and methods are disclosed for die access order variation to a memory having a multiple-die architecture. In certain embodiments, an apparatus may comprise a controller configured to assign a unique die access order to each set of multiple sets of related commands, a die access order controlling an order in which a plurality of dies of a solid state memory are accessed to perform the related commands. A first stream may be assigned a first die access order, and a second stream may be assigned a second, different die access order, thereby distributing the timing of die access collisions between the streams.