Memory Sub-System Queue Snapshot Recovery After Communication Errors
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Solution Overview
Problem
Traditional memory sub-systems handle communication errors by entering a panic state, rendering the device temporarily unusable and inaccessible, leading to significant downtime and data loss, especially in critical environments like servers and enterprises, with limited diagnostic information and high dependency on manufacturer intervention.
Innovation Solution
A recovery flow is implemented that avoids the panic state by storing controller register snapshots, suspending command processing, flushing the queue, and performing recovery actions, providing detailed diagnostic information to maintain device operation and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional panic state handling is used for communication errors, then device safety is protected by halting operations, but device accessibility and operational continuity are lost leading to significant downtime
Solution Approach 1:
The system performs preliminary actions by capturing and storing snapshots of controller registers and command queues before entering error handling mode. This preparation enables rapid recovery without full system halt, as the diagnostic information is already preserved and the system can resume operations after error resolution.
Solution Approach 2:
The error handling approach transitions from a static panic state (complete halt) to a dynamic recovery flow that allows selective suspension of command processing while maintaining device accessibility. The system can dynamically switch between operational states based on error severity, enabling continued read access even during write error recovery.
2Reliability
If traditional panic state handling is used, then error containment is achieved by halting all operations, but diagnostic information is limited and manufacturer intervention is required
Solution Approach 1:
The system captures snapshots of controller registers and command queues before error handling begins, preserving diagnostic information about the error state, ongoing operations, and system context. This preliminary data collection enables comprehensive error analysis without requiring manufacturer intervention.
Solution Approach 2:
The system implements feedback mechanisms by logging detailed error information including register states, command queues, and recovery outcomes. This feedback loop provides continuous diagnostic data that enables autonomous error resolution and reduces dependency on manufacturer support.
3Stability of the object's composition
If traditional panic state is entered, then system stability is maintained by preventing further operations, but device accessibility is completely lost
Solution Approach 1:
The error handling system segments the suspension of operations selectively - only command processing is suspended while read operations and diagnostic access remain available. This segmentation maintains device accessibility for critical functions while preventing operations that could exacerbate the error condition.
Solution Approach 2:
The system changes operational parameters by transitioning from a complete operation halt (panic state) to a selective operation suspension (recovery flow). This parameter change allows the system to maintain accessibility for read and diagnostic operations while restricting write and command operations during error recovery.
Data Source
AI summary
A communication error between a memory sub-system controller and a memory device is detected. Based on the communication error being detected, execution of command processing by the memory sub-system controller is suspended. Command data comprising a snapshot of a command queue of the memory sub-system controller is stored. The command queue comprises one or more commands. The command queue is flushed. The memory sub-system is returned to a normal state of operation. One or more recovery actions are performed to attempt recovery of the memory device. Based on determining recovery of the memory device is unsuccessful, affected portions of the memory device are marked as retired. The one or more commands from the command queue are reissued.