Host Dual-Write Buffering for External SSD Data Loss Prevention
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Solution Overview
Problem
Data loss occurs when an external data storage device cannot keep up with the data generation rate of a host, leading to buffer overflows and frame drops during high-data-rate operations, such as video recording, due to the lack of a back-pressure mechanism.
Innovation Solution
Implementing a dual-write method where data is initially stored in the host's non-volatile memory and then copied to the external storage device, using hashing techniques to confirm successful storage and releasing the host's copy only after acknowledgment, thereby preventing data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written directly to external storage device without backup, then storage capacity is utilized efficiently, but data loss occurs when storage device cannot keep up with data generation rate
Solution Approach 1:
The host performs preliminary actions by storing data in its non-volatile memory before the external storage device is ready to receive it. This advance preparation ensures data is safely captured and can be transferred later without loss, resolving the contradiction between reliability and complexity by adding a preparatory buffering step.
Solution Approach 2:
The host's non-volatile memory acts as an intermediary between the data source and the external storage device. This intermediate storage layer buffers data when the external device cannot keep up with the data generation rate, preventing data loss while managing complexity through controlled data flow.
2Reliability
If data is buffered in host memory until external storage is ready, then data loss is prevented, but memory resources are consumed
Solution Approach 1:
The host discards data from its non-volatile memory once the external storage device has successfully received and confirmed the data. This recovery of memory resources allows the system to maintain data integrity while minimizing long-term memory consumption through a write-back mechanism.
Solution Approach 2:
The external storage device provides feedback to the host when data has been successfully received and stored. This feedback mechanism allows the host to know when to release buffered memory resources, resolving the contradiction between maintaining data integrity and managing memory resource consumption.
3Reliability
If dual-write method is implemented with copy and verify, then data integrity is ensured, but write amplification increases
Solution Approach 1:
The system performs a partial dual-write operation where data is first written to the host's non-volatile memory, and then conditionally copied to the external storage device only when needed. This selective copying reduces overall write amplification compared to always duplicating writes, while still ensuring data integrity through the verify-and-copy mechanism.
Data Source
AI summary
A host may not have a large enough internal non-volatile memory to store generated data, such as video. In such situations, the host can store the data in an external data storage device, such as an external solid-state drive (SSD). However, if the storage rate of the external data storage device drops below the rate at which the host is generating and sending the data to the external data storage device, data loss can occur. To help avoid this situation, the host can use a dual-write method in which a portion of the data is both sent to the external data storage device for storage and written in the host's internal non-volatile memory. That way, if the portion of the data sent to the external data storage device is lost, the portion of the data can be resent from the host's internal non-volatile memory.