Extending Logical-to-Physical Table for NVMe Garbage Collection
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Solution Overview
Problem
NVMe SSDs in datacenters experience unpredictable performance due to wear and the need for garbage collection, which can strain host devices and disrupt I/O operations, as the duration of garbage collection varies with the number of bad blocks.
Innovation Solution
Implementing an extendable logical-to-physical (L2P) region technique that allows a portion of the L2P table to be mapped to an extended physical region on peer NVMe SSDs, enabling garbage collection to be performed externally, thereby reducing the computational burden on host devices and maintaining consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If garbage collection is performed by the NVMe SSD itself, then the storage device can manage its own memory blocks, but the I/O performance becomes unpredictable due to variable garbage collection duration
Solution Approach 1:
The patent extracts the L2P table from the NVMe SSD and stores it externally in host memory or a separate storage device. This allows the SSD to perform garbage collection without being constrained by the need to maintain an up-to-date L2P table locally, thereby enabling predictable I/O performance while maintaining productivity.
Solution Approach 2:
The patent performs preliminary actions by pre-allocating and pre-synchronizing the L2P table in advance before garbage collection is needed. This ensures that the L2P table is ready and available when garbage collection starts, eliminating delays and ensuring predictable performance throughout the garbage collection process.
2Speed
If the L2P table is stored locally in the NVMe SSD, then address mapping is fast and efficient, but the SSD cannot perform garbage collection without disrupting I/O operations
Solution Approach 1:
The L2P table is extracted from the NVMe SSD and stored externally. This separation allows the SSD to access the L2P table quickly through external memory interfaces while simultaneously performing garbage collection operations without disrupting I/O operations, as the L2P table updates do not block the I/O path.
Solution Approach 2:
The patent introduces an intermediary mechanism where the host system or a separate storage device manages the L2P table. This intermediary allows the SSD to perform garbage collection while the host or external device maintains the L2P table, enabling both fast address mapping and continuous I/O operations.
3Reliability
If Open-Channel SSD with host-side FTL is used, then predictable performance is achieved, but the host device bears the computational burden of garbage collection
Solution Approach 1:
The patent segments the FTL functionality between the host and the SSD. The host manages the L2P table while the SSD handles garbage collection operations. This segmentation allows predictable performance to be achieved without placing the full computational burden on the host, as the SSD independently manages its own garbage collection processes.
Solution Approach 2:
The SSD performs self-service by autonomously managing its own garbage collection operations while the host maintains the L2P table. This self-service approach allows the SSD to handle its own maintenance tasks without requiring intensive host intervention, reducing host computational load while maintaining performance consistency.
Data Source
AI summary
A data storage device coupled to a controller. The controller is configured to determine whether a request to perform a data transfer operation has been received and determine whether a request to perform a garbage collection operation is necessary during the data transfer operation. The controller generates an extended logical-to-physical table (L2P) including information for the data transfer operation in response to determining the request to perform the data transfer operation has been received and the request to perform the garbage collection operation is necessary, transmits the extended L2P table to one or more peer data storage devices, and performs the garbage collection operation after transmitting the extended L2P table to the one or more peer data storage devices.