Open-Channel SSD Data Copying Bypassing Host Interface
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Solution Overview
Problem
The bandwidth of non-volatile memory (NVM) storage devices, such as SSDs, is limited by the host interface, particularly the PCIe interface, which restricts the performance of data access, especially for random address access, and existing interfaces do not efficiently manage internal parallelism in open-channel SSDs.
Innovation Solution
A method for copying data between open-channel SSDs involves a host transmitting read and initialize commands to source and destination SSDs, with the SSDs performing read operations, specifying data buffer addresses, copying data, and storing it in a data buffer or NAND block, and reporting results through submission and completion queues, optimizing data transfer and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a PCIe interface is used for the host interface of the NVM storage device, then the bandwidth of the storage device is improved, but the bandwidth is still limited by the host interface
Solution Approach 1:
The patent introduces an intermediary data buffer in the destination SSD and a direct SSD-to-SSD data path that bypasses the host interface. The source SSD writes data directly to the destination SSD's data buffer through a dedicated interface, eliminating the host interface bandwidth bottleneck for data transfer operations while the host interface continues to handle control commands.
2Productivity
If a multi-queue structure is implemented in the NVMe interface, then I/O parallelism is increased, but the complexity of interface management increases
Solution Approach 1:
The patent segments the data transfer operation into independent queue-based units. Each I/O request can be assigned to a specific queue in the multi-queue structure, allowing parallel processing of multiple data transfers between different SSD pairs. The segmentation enables the system to manage complexity by handling multiple operations independently through separate queues rather than as a single complex operation.
Solution Approach 2:
The source and destination SSDs autonomously manage the data transfer process without requiring continuous host intervention. The SSDs self-manage the multi-queue operations, including queue selection, data buffer management, and transfer coordination, reducing the management burden on the host system while utilizing the parallelism benefits of the multi-queue structure.
3Ease of operation
If data copying is performed through the host interface, then the host can manage the transfer, but the system memory bus burden increases and transfer efficiency decreases
Solution Approach 1:
The patent introduces a direct SSD-to-SSD data path as an intermediary channel that bypasses the host interface for actual data transfer. The host retains management control through command issuance and completion notification, while the data itself flows through a dedicated buffer and interface between SSDs, eliminating the memory bus burden.
Solution Approach 2:
The patent extracts the data transfer function from the host interface path and creates a separate dedicated data path between SSDs. The host interface is taken out of the data transfer path and retains only control and status functions, while the data buffer and transfer mechanism are extracted as an independent subsystem that operates autonomously between storage devices.
Data Source
AI summary
Disclosed is a method of copying data between open-channel solid state drives (SSDs), the method including transmitting, by a host, a read command to a source SSD, performing, by the source SSD, a read operation on data stored in the source SSD, in response to the read command, specifying, by the source SSD, an address of a data buffer of a destination SSD, in response to the read command, copying, by the source SSD, the stored data to the specified address of the data buffer, and storing, by the destination SSD, the data copied from the source SSD.