File System Size Reduction Without Volume Shrink
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Solution Overview
Problem
In clustered storage environments, shrinking the size of a file system without close coordination with underlying storage is challenging due to difficulties in managing data block movement across multiple NAS data storage nodes supporting various block storage technologies.
Innovation Solution
Deploying a file system on a local volume with a thin volume configuration, where the file system user size is initially set equal to the local volume size, allowing it to be reduced later without shrinking the volume, by extending or reducing the file system size based on storage needs, and unmapping unused blocks in the background.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the file system size is reduced by shrinking the volume, then the storage space is freed up, but the coordination complexity across multiple NAS data storage nodes increases
Solution Approach 1:
The patent segments the volume into slices, where each slice can be independently managed. This allows the file system to reduce its size by unassigning slices rather than shrinking the entire volume, thereby freeing storage space without requiring complex coordination across all nodes for a global shrink operation.
Solution Approach 2:
The patent extracts the volume shrink operation from the file system shrink operation. By using thin volumes and slice-based management, the system can reduce file system size by simply unassigning slices that are no longer needed, separating the volume management from the file system management and reducing coordination complexity.
2Volume of moving object
If the volume is shrunk by moving data blocks to other slices, then the file system size is reduced, but the operational coordination requirement increases
Solution Approach 1:
The patent performs preliminary actions by pre-creating thin volumes with sufficient capacity and pre-dividing them into slices. When the file system needs to be shrunk, the system simply unassigns slices that are no longer needed, rather than performing complex data block movements, thereby reducing operational coordination requirements.
Solution Approach 2:
The thin volume mechanism allows the file system to self-manage its size by unassigning slices as needed, without requiring extensive coordination with the underlying storage system. The system serves itself by using the slice assignment table to track and manage which slices are in use, eliminating the need for complex coordinated shrink operations.
3Device complexity
If thin volume is used to avoid close coordination with underlying storage, then the management complexity is reduced, but the storage space allocation flexibility is limited
Solution Approach 1:
The patent introduces dynamic slice assignment where slices can be assigned and unassigned based on real-time file system needs. The slice assignment table is dynamically updated when files are created or deleted, allowing the system to adapt storage space allocation flexibly without close coordination with the underlying storage system.
Solution Approach 2:
The system uses feedback from file system operations (file creation, deletion, access patterns) to dynamically adjust slice assignments. When files are deleted or space is no longer needed, the system receives feedback and unassigns corresponding slices, providing flexible storage space allocation while maintaining simple management through the slice assignment table.
Data Source
AI summary
Techniques for limiting storage consumed by a file system without shrinking a volume upon which the file system is deployed. The techniques are employed in a clustered environment including multiple NAS nodes, each having access to block storage including multiple storage devices. By deploying the file system on a volume of a NAS node within the clustered environment, setting the value of the FS user size to be equal to the FS volume size, and if, at a later time, it is desired to reduce the file system size, setting the value of the FS user size to a lesser value than the FS volume size, IO requests received at the NAS node can be satisfied within the logical limit of the lesser value of the FS user size without shrinking the local volume, allowing the file system size to be reduced without requiring close coordination with the block storage.