Differential Bitmap Copy System for Fast Reliable Data Synchronization
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Solution Overview
Problem
The increasing number of volumes and volume capacity in storage systems leads to longer initial copy times in remote copy systems, and existing differential copy technologies lack reliability due to unconfirmed differential data reflection between primary and secondary volumes.
Innovation Solution
A copy system and method that utilize bitmaps to manage data areas, create differential bitmaps, and synchronize valid data copying between primary and secondary volumes, ensuring accurate data reflection and preventing copy omission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If differential copy technology is applied to initial copy, then the initial copy time is reduced, but the reliability of data reflection confirmation is insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the secondary storage apparatus sends back a response bitmap to the primary storage apparatus after receiving the differential bitmap. This response bitmap confirms whether the differential data has been successfully written, allowing the primary side to verify data reflection status and retransmit if necessary, thus ensuring reliability while maintaining fast differential copy performance
Solution Approach 2:
The patent introduces a response bitmap as an intermediary verification mechanism between the primary and secondary storage apparatuses. This intermediary structure enables reliable confirmation of data reflection without requiring full data retransmission, resolving the contradiction between speed and reliability
2Reliability
If all areas of primary volume are copied to secondary volume, then data completeness is ensured, but the initial copy time increases significantly
Solution Approach 1:
The patent extracts only the differential portions of data that have changed since the last copy operation, rather than copying all data. By using bitmaps to identify and transfer only the modified areas, it significantly reduces initial copy time while maintaining data completeness through subsequent verification mechanisms
Solution Approach 2:
The patent applies partial action by copying only the necessary differential data portions identified by the bitmap rather than performing a complete copy of all volume areas. This selective approach reduces copy time while the verification process ensures data completeness
Data Source
AI summary
Proposed are a copy system and a copy method capable of performing initial copy in a short amount of time and with high reliability. On a primary side, the area in the first volume to which data was written from the host is managed, a second bitmap is created reflecting the contents of the first bitmap, and the second bitmap is sent to the secondary side on the primary side. On a secondary side, a third bitmap to which the second bitmap sent from the primary-side is merged is created, on the primary side, only the valid data containing data written by the host in the first volume is copies to the second volume based on the second bitmap, and, on the secondary-side, the differential between the first and second volumes during the initial copy is managed based on the third bitmap.