Storage Controller Zone Command Prioritization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In flash storage devices with Zoned Namespace (ZNS), multiple zones sharing the same underlying resources experience latency issues due to command starvation, where one zone's commands can delay the execution of another zone's commands, preventing the achievement of intended speed or latency requirements.
Innovation Solution
The storage device employs a controller that prioritizes and allocates commands based on zone properties and utilization states, using essential and optional resources to interleave command execution and balance resource utilization across zones, ensuring that each zone meets its minimum requirements while allowing for maximum bandwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple zones share the same underlying resources (dies or channels) to improve device utilization and reduce complexity, then resource efficiency is improved, but command execution latency increases due to command starvation and resource contention
Solution Approach 1:
The patent implements dynamic command prioritization where the controller adjusts command execution priority based on real-time zone requirements and resource utilization states. Commands from zones with stricter latency requirements or higher priority levels are elevated in the execution queue, allowing the system to adaptively balance resource sharing with latency guarantees without dedicated physical separation.
Solution Approach 2:
The system changes operational parameters by introducing zone priority levels and utilization state thresholds. When a zone's resource utilization exceeds certain thresholds or its commands exceed latency deadlines, the controller modifies execution parameters by boosting priority of pending commands from that zone, thereby dynamically adjusting time-sharing ratios to prevent starvation while maintaining resource efficiency.
2Productivity
If the flash storage device utilizes all dies for a single command to maximize bandwidth utilization, then throughput is improved, but subsequent commands from other zones experience delayed execution and higher latencies
Solution Approach 1:
The controller implements periodic sampling of zone utilization states and command queue depths. At regular intervals, it reassesses which zones require resource allocation and adjusts command prioritization accordingly. This periodic intervention prevents any single zone from monopolizing all dies for extended periods, ensuring that bandwidth is utilized efficiently while periodically redistributing resources to maintain acceptable execution speeds for all zones.
Solution Approach 2:
The system allows temporary excessive resource allocation to high-priority zones when their utilization state indicates urgent need, but limits this allocation to prevent complete starvation of other zones. The controller may allocate more than the average share of dies to a particular zone during critical periods, but implements caps or time-limits on such allocations to ensure overall system throughput and fairness.
Data Source
AI summary
Aspects of a storage device including a memory and a controller are provided which re-prioritize commands based on zone properties. The controller receives from a host commands associated with a plurality of zones, allocates the memory into a plurality of zone resources based on zone properties indicated by the host for the zones, and identifies a utilization state of the memory for one of the zones. The controller changes a priority order of the commands based on the zone properties and the utilization state for the one of the zones. The controller then executes the commands in the memory or zone resources according to the priority order. As a result, execution of commands may be balanced between zones and lower latencies may be achieved overall for each zone. Improved performance or throughput of the storage device in handling zone commands may therefore result.