Snapshot Virtual Storage Allocation for Faster Garbage Collection
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Solution Overview
Problem
The existing snapshot methods in storage systems, such as the redirect on write (RoW) method, face inefficiencies in garbage collection and decreased throughput due to increased mapping information updates during read and write IO processing, particularly when addressing duplicate data across multiple snapshot families.
Innovation Solution
A storage system and method that utilizes a snapshot virtual device for primary and snapshot volumes, compresses data in a compression virtual device, and switches between overwriting and new allocation based on data size for efficient resource utilization, reducing the time required for address mapping changes during garbage collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a virtual device space is added to separate shared data from independent data, then garbage collection efficiency is improved, but mapping information increases and storage controller load increases
Solution Approach 1:
The patent divides the virtual device space into two distinct segments: a first virtual device space for shared data and a second virtual device space for independent data. This segmentation allows garbage collection to operate more efficiently on the shared data portion while maintaining separate mapping information for each space, thereby reducing the overall complexity compared to managing all data in a single undifferentiated space.
Solution Approach 2:
The patent extracts shared data from the conventional storage location and places it in a dedicated first virtual device space. This extraction enables targeted garbage collection operations on shared data without affecting independent data operations, improving garbage collection efficiency while the separate virtual device spaces help manage mapping information complexity.
2Measurement precision
If mapping information is increased to track data across multiple snapshot families, then data tracking accuracy is improved, but processing time increases
Solution Approach 1:
The patent segments the snapshot family structure by introducing a first snapshot family for shared data and a second snapshot family for independent data. This segmentation enables more precise tracking of data relationships within each family while reducing the overall processing time by allowing parallel or independent management of the two families, rather than treating all snapshot data as a single complex structure.
Data Source
AI summary
A processor uses a snapshot virtual device as a storage destination for data of a primary volume and a snapshot volume, compresses data stored in the snapshot virtual device and stores the compressed data in a compression virtual device, and stores the data stored in the compression virtual device in a storage device. When a write request is received from a host, the processor switches, according to a size of an address range of a write destination, between overwriting processing of overwriting an area on the snapshot virtual device which is allocated to large-size data and new allocation processing of allocating a new area on the snapshot virtual device to the address range of the write destination for small-size data, and compresses a plurality of pieces of small-size data stored in the new area and collectively stores the plurality of pieces of small-size data in the compression virtual device.