Hierarchical Virtual Address Space Expansion for Flash Garbage Collection
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Solution Overview
Problem
The performance of storage apparatuses is hindered by the heavy load associated with garbage collection in all-flash arrays, which leads to decreased I/O performance due to the need to copy and erase data, resulting in inefficient use of flash memory.
Innovation Solution
The implementation of a storage apparatus with hierarchical address spaces that allows for the expansion of virtual address spaces without data movement, by allocating new address areas and managing them as usage prohibition areas, thereby reducing the load during garbage collection and enhancing I/O performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the storage controller performs garbage collection by copying valid data to new areas and erasing old data, then free storage areas are ensured, but the processing load increases and I/O performance deteriorates
Solution Approach 1:
The patent divides the storage address space into multiple hierarchical segments (real address space, first virtual address space, second virtual address space). This segmentation allows garbage collection to operate at the virtual address space level rather than requiring physical data movement, reducing the processing load while ensuring free storage areas are available when needed.
Solution Approach 2:
The patent introduces a second virtual address space as an intermediary layer between the first virtual address space and the real storage medium. This intermediary allows the system to manage storage allocation and garbage collection without direct data copying, as the virtual address space can be expanded and contracted logically without moving actual data, thus improving I/O performance.
2Quantity of substance
If the storage controller expands the virtual address space by adding new continuous address areas, then storage capacity increases, but the complexity of address management increases
Solution Approach 1:
The patent implements a nested hierarchical structure where the second virtual address space is nested within the first virtual address space, which in turn is nested within the real address space. Each layer manages a portion of the address space, allowing expansion of storage capacity while distributing the complexity of address management across multiple manageable layers rather than requiring a single complex management system.
Data Source
AI summary
A storage device allocates an address area of an address space to the first virtual address space in accordance with writing onto a first virtual address space. A controller manages an address area in the first virtual address space, in which address area a mapping to the real address space has been removed, as a usage prohibition area. When a use state of the first virtual address space reaches a predetermined criterion, the controller or the storage device adds new continuous address areas to the first virtual address space to expand the first virtual address space. The storage device allocates an area, in which a mapping to the first virtual address space has been removed, to the first virtual address space expanded.