Virtual Disk Image Copying via Snapshot and Difference Application
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Solution Overview
Problem
In virtualized systems, copying a disk image between storage devices requires shutting down the virtual machine and involves copying the entire image, which is inefficient and time-consuming.
Innovation Solution
A method that creates a snapshot of a disk image, copies this snapshot to another storage device, and then computes and applies the differences to create an up-to-date disk image without re-copying the entire image, allowing for efficient copying of virtual disks without shutting down the virtual machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire disk image is copied between storage devices, then the copied data is complete and accurate, but the copying process is time-consuming and requires shutting down the virtual machine
Solution Approach 1:
The patent segments the disk image copying process into three distinct phases: (1) creating a snapshot of the source disk image, (2) copying only the snapshot to the target storage device, and (3) computing and applying differences to synchronize changes. This segmentation allows the system to copy minimal data initially while maintaining data completeness through incremental updates.
Solution Approach 2:
The patent performs preliminary actions by creating a snapshot of the source disk image before the copying process begins. This snapshot serves as a baseline that can be copied quickly to the target device, eliminating the need to copy the entire disk image upfront. The snapshot is then used as the foundation for subsequent difference computations and incremental updates.
2Reliability
If the entire disk image is copied, then the target disk image is complete, but the process requires shutting down the virtual machine and consumes significant resources
Solution Approach 1:
The patent enables continuous operation of the virtual machine throughout the disk image copying process. By using snapshots and difference computations, the system maintains data accuracy while allowing the virtual machine to remain operational. The copying process occurs in the background without interrupting the virtual machine's useful actions, thus maintaining system productivity and availability.
Solution Approach 2:
The patent uses copying of snapshots instead of copying entire disk images. The snapshot is a point-in-time representation that can be copied efficiently to the target storage device. This copying approach maintains data accuracy by capturing the exact state of the source disk image at a specific moment, while significantly reducing the amount of data that needs to be transferred and processed.
3Ease of manufacture
If traditional copying methods are used, then the process is simple to implement, but it copies unnecessary data and consumes excessive resources
Solution Approach 1:
The patent extracts only the necessary data for copying by computing differences between the source disk image and the snapshot. Instead of copying the entire disk image, the system identifies and extracts only the changed blocks that need to be transferred to the target device. This extraction process significantly reduces computational resources and energy consumption while maintaining implementation feasibility through standardized difference computation algorithms.
Data Source
AI summary
A system and method are disclosed for efficiently copy a disk image between storage devices. In accordance with one example, a computer system issues a request to create on a first storage device a snapshot of a first disk image that is stored on the first storage device. The computer system then issues a request to create on the first storage device a second disk image based on the snapshot, and copies the snapshot on to a second storage device. The computer system issues a request to create on the second storage device a third disk image based on the snapshot. The computer system then issues a request to compute a difference between the second disk image and the snapshot, and the difference is overwritten on to the third disk image.