Bounded Latency Command Handling in Flash Translation Layer
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Solution Overview
Problem
Current methods for reducing latency in computer applications, such as SSD deployments, fail to guarantee latency limits due to factors like die collisions and long decode times, leading to user and processing delays, and do not account for initial command processing times and system operations.
Innovation Solution
Implementing a method where commands are timestamped and added to a queue with a timer set according to a required latency threshold, allowing for timely notification of latency exceedance and enabling flexible latency settings across various uses, ensuring bounded latency without exceeding predefined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If multiple sources for data are used to limit latency, then data availability is improved, but system complexity and processing overhead increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing metadata about multiple data sources, their locations, and access characteristics before latency issues arise. When a read command arrives, the system can immediately query this pre-prepared information to determine the best source, avoiding complex real-time analysis and reducing latency while maintaining manageable system complexity
Solution Approach 2:
The patent introduces an intermediary component (the latency management module with metadata store) that mediates between the host and multiple data sources. This intermediary pre-processes information about available data sources and makes rapid source selection decisions, reducing the complexity burden on the overall system while enabling fast data retrieval from appropriate sources
2Reliability
If recovery processes such as soft bit decode or XOR recovery are implemented, then data retrieval reliability is improved, but latency increases due to processing time
Solution Approach 1:
The patent applies dynamics by making the recovery process adaptive and conditional rather than static and mandatory. The system dynamically evaluates whether recovery is necessary and feasible within latency constraints by checking metadata about data availability and current system state. Recovery processes like soft bit decode or XOR recovery are only invoked when metadata indicates they will meet latency requirements, otherwise alternative data sources are selected
Solution Approach 2:
The patent uses preliminary action by pre-calculating recovery feasibility and storing this information in metadata before recovery is actually needed. The system pre-assesses whether soft bit decode or XOR recovery can complete within acceptable latency windows based on historical performance data and current system state, allowing rapid decision-making without complex real-time analysis
3Measurement precision
If initial command processing times and system operations are accounted for, then latency accuracy is improved, but system complexity increases
Solution Approach 1:
The patent extracts and isolates the complexity of latency calculation into a separate metadata management component. Instead of embedding complex latency prediction logic throughout the entire storage system, the patent creates a dedicated metadata store that pre-calculates and stores latency estimates for various operations. This separation allows accurate latency accounting while keeping the main processing paths simple and manageable
Data Source
AI summary
The present disclosure generally presents a method and apparatus to provide a bounded latency, where a device would report “non-service” of a command at the defined system level timeout or earlier if the device was unable to successfully return the data to the host.