Storage System Snapshot Virtual Device Resource Management
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Solution Overview
Problem
The existing storage systems face challenges in maintaining high throughput due to increased load on storage controllers from virtual device mapping and metadata management, leading to reduced performance and limited volume creation capabilities.
Innovation Solution
A storage system that manages primary and snapshot volumes as a snapshot family, using a snapshot virtual device to switch between overwrite and new allocation processes based on write destination address ranges, optimizing virtual device resource usage and reducing metadata updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a virtual device space is added to manage snapshot families, then snapshot functionality is improved, but the load on storage controller increases and throughput decreases
Solution Approach 1:
The patent divides the storage system into distinct components: primary volumes, snapshot volumes, and a shared pool volume. By segmenting snapshot data from primary volume data and managing them separately with independent metadata, the system reduces the mapping overhead that would otherwise burden the storage controller during I/O operations, thereby maintaining throughput while enabling snapshot functionality.
Solution Approach 2:
The patent introduces a pool volume as an intermediary storage space that holds snapshot data separately from primary volumes. This intermediary structure allows snapshot operations to be performed without directly impacting primary volume I/O paths, reducing controller load and maintaining throughput while still providing snapshot capabilities.
2Adaptability or versatility
If virtual device resources are increased to support more volumes, then volume creation capability is improved, but metadata overhead increases and available resources are reduced
Solution Approach 1:
The patent merges multiple snapshot volumes into a single shared pool volume. Instead of allocating separate virtual device resources for each snapshot, the system consolidates snapshot storage in one pool, reducing metadata overhead and virtual device resource consumption while still supporting multiple snapshot volumes through logical management of the shared pool.
3Reliability
If data is written to new areas without overwriting (rewrite method), then data integrity is improved, but fragmentation increases and performance degrades
Solution Approach 1:
The patent implements a copy-on-write mechanism where snapshot data is copied to the pool volume when changes occur. This approach maintains data integrity by preserving original data while creating snapshots, and by managing writes to the pool volume separately from primary volumes, it avoids fragmentation issues that would degrade performance.
Data Source
AI summary
The present invention achieves high throughput by making efficient use of virtual device resources. A storage system includes a storage device and a processor. The processor manages a primary volume and a snapshot volume as a snapshot family. The processor uses a snapshot virtual device as the data storage destination for the primary volume and for the snapshot volume. Upon receiving a write request from a host, the processor switches between an overwrite process and a new allocation process in accordance with the reference made to a write destination address range by the snapshot volume and with the degree of distribution of the write destination address range in the snapshot virtual device. The overwrite process is performed to overwrite an allocated area of the snapshot virtual device. The new allocation process is performed to allocate a new area of the snapshot virtual device to the write destination address range.