Cooperative Physical Defragmentation in Flash Storage
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Solution Overview
Problem
Conventional storage systems face inefficiencies in physical defragmentation of data stored in storage devices like NAND flash memory, as they primarily focus on logical defragmentation, leading to fragmented data in physical address spaces, which hampers quick and efficient data access.
Innovation Solution
A storage system that performs physical defragmentation cooperatively between a host and a storage device, where the host reads fragmented data and writes it continuously into new physical regions, utilizing a controller and flash memory unit to manage physical blocks and implement garbage collection and defragmentation operations, ensuring sequential data storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If logical defragmentation is performed by the file system, then logical address sequentiality is improved, but physical address fragmentation remains and data access speed is limited
Solution Approach 1:
The patent segments the defragmentation process into two distinct phases: logical defragmentation (performed by the file system to ensure LBA sequentiality) and physical defragmentation (performed by the storage device to ensure physical address continuity). This segmentation allows each component to optimize for its specific function, with the storage device controller handling physical block reorganization independently to improve data access speed without compromising logical address organization.
Solution Approach 2:
The storage device controller acts as an intermediary between the file system and the physical storage medium. It receives logical defragmentation results from the file system and performs additional physical defragmentation by remapping data blocks to contiguous physical addresses, thereby mediating between logical address space management and physical storage efficiency to enhance data access speed.
2Adaptability or versatility
If data is rewritten frequently in NAND flash memory, then data updates are achieved, but physical fragmentation increases and storage efficiency decreases
Solution Approach 1:
The patent implements preliminary physical defragmentation by the storage device controller before data is significantly fragmented. The controller continuously monitors physical address distribution and performs proactive remapping operations to maintain physical contiguity, preventing fragmentation from occurring in the first place rather than correcting it after it develops, thereby maintaining high storage efficiency during frequent data updates.
Solution Approach 2:
The storage device controller performs self-service physical defragmentation independently without requiring host system intervention. It autonomously identifies fragmented data blocks, allocates new contiguous physical addresses, and remaps the data, enabling the storage device to maintain its own optimization state while the host system continues normal read/write operations, thus preserving storage efficiency during frequent updates.
3Ease of operation
If conventional logical defragmentation alone is used, then file system management is simple, but physical data fragmentation hampers efficient data access
Solution Approach 1:
The patent extracts the physical defragmentation function from the file system and assigns it to the storage device controller. The file system continues to handle only logical address space management, maintaining its simplicity, while the storage device controller independently performs physical block reorganization to eliminate physical fragmentation, thereby reducing data access time without complicating file system operations.
Solution Approach 2:
The storage device controller serves as an intermediary layer between the simple file system and the physical storage medium. It transparently performs physical defragmentation operations without requiring changes to file system logic or user operations, thereby maintaining ease of file system management while simultaneously reducing data access time through optimized physical data organization.
Data Source
AI summary
A storage system includes a host including a processor and a storage device including a controller and a flash memory unit. The host is configured to read physically fragmented data of a file stored in one or more physical storage regions of the flash memory unit and write the data continuously into other one or more physical regions of the flash memory unit, such that the data are physically defragmented.