Storage Controller Block Recovery During Ungraceful Shutdown
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Solution Overview
Problem
Data storage devices face issues with data integrity and reliability due to consecutive power loss events, leading to depletion of available memory blocks and inability to accept new data, as existing power loss protection mechanisms like capacitors are insufficient.
Innovation Solution
A data storage device with a controller that detects power loss events, issues alerts to the host device about block recovery status, monitors free block counts, and determines if blocks can be continuously programmed, allowing for efficient block usage and communication during ungraceful shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitors are used to preserve power for handling power loss events, then data integrity is improved, but the available memory blocks are depleted due to consecutive power loss events
Solution Approach 1:
The controller implements a feedback mechanism by sending block busy alerts to the host device when blocks are affected by power loss events and block ready alerts when blocks are recovered. This feedback loop allows the host to adjust its data writing behavior, preventing further block depletion while maintaining data integrity through proper power loss handling.
Solution Approach 2:
The controller acts as an intermediary between the host device and the memory blocks affected by power loss. It manages the recovery process of incomplete blocks and communicates their status to the host, mediating between the need for data integrity (completing blocks) and the need to preserve available blocks for future operations.
2Productivity
If the data storage device chooses a new block to write data to while abandoning the original block during power recovery, then the device can continue operating, but the block count depletes until the device enters read-only mode
Solution Approach 1:
The controller performs preliminary assessment of blocks affected by power loss events to determine their recoverability before abandoning them. By evaluating whether blocks can be successfully recovered and notifying the host in advance, the system avoids unnecessary block abandonment and preserves the block count while maintaining operational continuity.
Solution Approach 2:
The controller implements self-service by autonomously managing the recovery process of incomplete blocks after power loss, determining their status, and communicating with the host device. This self-management reduces the need for the host to intervene by choosing new blocks, thereby preserving block count while ensuring continuous operation.
3Reliability
If the controller monitors free block counts and issues warnings, then the host device can be alerted before power loss halt is triggered, but the system complexity increases
Solution Approach 1:
The controller monitors the free block count as a critical parameter and triggers warnings when it falls below predetermined thresholds. This parameter-based approach provides a simple and effective mechanism for maintaining device reliability by alerting the host before critical block depletion occurs, without requiring complex communication protocols.
Data Source
AI summary
The present disclosure generally relates to efficient block usage after ungraceful shutdown (UGSD) events. After a UGSD event, a host device is alerted by the data storage device that a QLC block that was being used prior to the UGSD event is experiencing an ongoing block recovery and that the block is not yet available to accept new data. The block is then checked to determine whether the block can continue to be used for the programming that was occurring at the time of the UGSD event. Once a determination is made, the data storage device notifies the host device so that normal operations may continue. Additionally, the amount of free blocks available for programming is monitored during UGSD events so that the host device can be warned if a power loss halt is triggered.