Storage System Redundancy via Journal Data Segmentation
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Solution Overview
Problem
Existing storage systems face challenges in maintaining redundancy and data integrity with a simple configuration, particularly when one storage control device stops operating, due to increased load on secondary devices and structural complexity in managing journal data and volume synchronization.
Innovation Solution
A storage system with multiple storage control devices, where each device manages data volumes and journal data differently, using differential management tables to synchronize data and reduce load, allowing seamless switching between devices and maintaining redundancy without complex volume copying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one secondary storage control device generates journal data for all data updates from the primary storage control device, then redundancy is maintained, but the load on that secondary device increases and structural complexity increases
Solution Approach 1:
The patent divides the journal data generation function among multiple secondary storage control devices. Each secondary device generates journal data only for the data updates it receives from the primary device, rather than one device handling all journal data generation. This segmentation reduces the load on individual devices and simplifies the overall structure.
Solution Approach 2:
Multiple secondary storage control devices work together to maintain redundancy. Each device maintains its own data copy and generates its own journal data, combining their efforts to provide system-wide redundancy without requiring a single device to handle all journaling responsibilities.
2Reliability
If volume copy processing is performed to synchronize storage contents between primary and secondary devices, then data integrity is maintained, but the period during which contents are not coincident becomes long and additional volume preparation is required
Solution Approach 1:
The patent extracts the synchronization mechanism from traditional volume copy processing. Instead of copying entire volumes periodically, the system uses journal data to apply only the necessary data updates to secondary devices, significantly reducing synchronization time and eliminating the need for pre-prepared volume copies.
Solution Approach 2:
The system prepares journal data in advance at the primary storage control device for each data update. This preliminary action allows secondary devices to quickly apply updates without needing to perform time-consuming volume copy operations, reducing the synchronization period.
Data Source
AI summary
A storage system secures system redundancy through a simple configuration. A primary storage control device and first secondary storage control device are connected by a synchronous method, and the primary storage control device and a second secondary storage control device are connected by an asynchronous method. The primary storage control device sets control numbers for update data, and saves journal data. The primary storage control device transmits the update data to the first secondary storage control device. The first secondary storage control device writes update data to a first secondary volume, and uses a plurality of bitmap tables to manage differences. If the primary storage control device stops operation, the first secondary storage control device becomes the new primary storage control device. Differential copying is performed from the first secondary storage control device to the second secondary storage control device.