Virtual Disk Synchronization Using Change Map and Hashing
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Solution Overview
Problem
Existing virtual machine synchronization technologies face inefficiencies in maintaining identical virtual disk contents across multiple machines, particularly in reducing data transmission and handling different internal formats, which can lead to discrepancies during synchronization.
Innovation Solution
A synchronization mechanism that uses a disk change map to track changed blocks on one virtual disk and only transmits the corresponding data to another virtual disk, employing a hash algorithm to determine data similarities and optimize data transfer, ensuring that only unique data is sent and committed, thereby maintaining identical virtual disk contents across machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complete virtual disk contents are transmitted during synchronization, then data integrity is ensured, but data transmission volume increases and synchronization efficiency decreases
Solution Approach 1:
The virtual disk is divided into blocks, and the synchronization process transmits only changed blocks rather than the entire disk contents. The disk change map tracks which blocks have been modified since last synchronization, enabling selective data transmission to maintain integrity while improving efficiency.
Solution Approach 2:
Only the essential changed portions of data are extracted and transmitted during synchronization. The system identifies and transmits solely the blocks that have changed, excluding unchanged data from the transmission process, thereby reducing bandwidth usage while maintaining data integrity.
2Reliability
If all blocks are transmitted during synchronization, then data completeness is ensured, but transmission time increases
Solution Approach 1:
The system maintains a disk change map that continuously tracks which blocks have been modified since last synchronization. This preliminary tracking action enables the system to quickly identify only the changed blocks during synchronization, avoiding the need to transmit the entire disk and significantly reducing synchronization time while ensuring completeness.
Solution Approach 2:
By segmenting the disk into blocks and tracking changes at the block level, the system can perform targeted synchronization of only modified segments, reducing the overall time required to complete the synchronization process while maintaining data completeness.
3Speed
If data is transmitted without comparison, then transmission speed is maintained, but data redundancy increases
Solution Approach 1:
The system uses hash algorithms to compare data blocks between the source and destination virtual disks before transmission. This feedback mechanism identifies blocks with identical content, allowing the system to skip transmitting redundant data while maintaining high transmission speed for actual changes.
Solution Approach 2:
The system extracts and transmits only the changed blocks after comparing hash values, eliminating redundant data transmission. By using hash comparison to identify unchanged blocks, the system avoids transmitting duplicate data while maintaining efficient transmission speeds for the necessary changes.
Data Source
AI summary
A mechanism is provided to maintain multiple copies of a virtual disk associated with a virtual machine by a synchronization function. The content of a first virtual disk is maintained, as a copy, at a second virtual disk by maintaining a record of the changes made to the first virtual disk and transferring only the changed data to the second. A disk change map represents the changed portions of the first virtual disk and is used to determine the content that must be transferred. Only data that differs between the two virtual disks is transferred thereby reducing the amount of data that needs to be transmitted.