SSD Controller HMB Loss Recovery via FTL Table Backup
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Solution Overview
Problem
Data storage devices, such as solid state drives (SSDs), face challenges in recovering from host memory buffer (HMB) loss, where the connection to the host memory buffer is disrupted, leading to potential data loss and system timeouts.
Innovation Solution
A data storage device with a controller configured to determine HMB loss, load a flash translation layer (FTL) table from a memory device, generate updates, and re-enable command fetching, while marking commands with error conditions and copying FTL tables between the memory device and HMB upon connection restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If data storage devices use host memory buffer (HMB) to store control data, then device cost decreases and access speed improves, but reliability deteriorates due to connection issues and host device taking back HMB allocation
Solution Approach 1:
The controller proactively detects HMB connection loss before it causes data corruption, loads backup FTL tables from the memory device, and prepares recovery actions in advance. This preliminary detection and preparation prevents the reliability issue from manifesting as actual data loss or host timeout
Solution Approach 2:
The system maintains backup copies of FTL tables in the memory device and implements error marking mechanisms beforehand. When HMB connection is lost, these pre-prepared backups and error markers provide a cushion that allows recovery without compromising data integrity or causing host timeout
2Speed
If controller continuously monitors HMB connection status, then recovery speed improves, but device complexity increases
Solution Approach 1:
The controller implements a feedback mechanism that monitors HMB connection status and automatically triggers recovery actions when connection loss is detected. This feedback loop enables fast recovery by immediately responding to connection changes without requiring complex manual intervention or continuous active monitoring
3Reliability
If controller loads FTL tables from memory device upon HMB loss, then data integrity is maintained, but access time increases
Solution Approach 1:
The controller loads backup FTL tables from the memory device proactively when HMB connection is lost, before any data access operations are needed. This preliminary loading ensures that when recovery is needed, the FTL tables are already available, minimizing the actual access time loss
Data Source
AI summary
A data storage device includes a memory device and a controller coupled to the memory device. The controller is configured to determine that a connection to a host memory buffer (HMB) of a host device is lost, load a most recent copy of a flash translation layer (FTL) table from the memory device, generate one or more updates to the most recent copy of the FTL table, and re-enable command fetching. The controller is further configured to mark one or more commands in a command database with an error condition upon the determining. After a boot of the connection, the controller is further configured to copy the FTL tables from the memory device to the HMB, work on commands, save FTL table differences between the HMB and the memory device, and update the FTL tables in the memory device.