Atomicity Assurance for Bundled Data Metadata in 3D TLC NAND
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Solution Overview
Problem
Current storage systems face challenges in providing atomicity assurance for bundling data and metadata in 3D TLC NAND flash storage devices, as the out-of-bound region does not provide sufficient space for metadata, leading to issues with write amplification and reduced performance.
Innovation Solution
The system employs transient caching and tail identification to manage residual data in a data buffer, avoiding unnecessary write and read operations by appending data to the buffer and writing from it directly to the storage device, thereby reducing write amplification and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data and metadata are bundled together in one I/O operation, then atomicity assurance and I/O efficiency are improved, but the data length increases and may not align with standard block size
Solution Approach 1:
The patent segments the bundled data into multiple pages, where each page is aligned to standard block sizes. The data is divided into a first page containing a portion of the bundled data and a second page containing the remaining portion, allowing each segment to be written independently to the storage device while maintaining atomicity through the mapping structure.
Solution Approach 2:
The patent introduces a mapping dimension between logical page addresses (LPAs) and physical page addresses (PPAs). By creating mapping entries that associate LPAs with PPAs, the system handles variable-length bundled data across multiple physical pages while maintaining the logical atomicity of the original I/O operation.
2Reliability
If metadata is written to out of bound region in 2D planar NAND, then atomicity is achieved, but 3D TLC NAND lacks sufficient space in out of bound region
Solution Approach 1:
The patent moves metadata from the constrained out-of-bound region (2D space) to a new dimension - separate logical pages in the address space. By storing metadata in dedicated logical pages and using LPA-PPA mapping, the system overcomes the physical space limitations of 3D TLC NAND while maintaining atomicity assurance.
Solution Approach 2:
The patent segments metadata into separate logical pages distinct from data pages. This segmentation allows metadata to be stored in the main array space rather than relying on limited out-of-bound regions, enabling atomicity in 3D TLC NAND where traditional OOB storage is insufficient.
3Productivity
If separate I/O operations are used for data and metadata, then block size alignment is maintained, but write amplification increases and performance decreases
Solution Approach 1:
The patent merges data and metadata into a single bundled I/O operation that is processed atomically. By combining what were previously separate I/O operations into one unified operation with a single LPA-PPA mapping entry, the system reduces write amplification and improves performance while maintaining block size alignment through page segmentation.
Data Source
AI summary
One embodiment facilitates atomicity assurance for storing data and metadata in a data stream. The system receives a first stream of data to be written to a storage device, wherein the first stream includes a plurality of I/O requests associated with data and corresponding metadata. In response to determining that residual data associated with a preceding I/O request of the first stream exists in a data buffer: the system appends, to the residual data, a first portion of data from a current I/O request to obtain a first page of data; the system writes a remainder portion of the current I/O request to the data buffer to obtain current residual data; and the system writes the first page of data to the storage device. Thus, the system thereby facilitates atomicity assurance for storing the data and corresponding metadata of each I/O request of the first data stream.