Virtual Disk Version Control via Overlay Mounting Points
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Solution Overview
Problem
Existing virtual disk technologies lack efficient version control and concurrent access capabilities, limiting users' ability to revert to previous states or share multiple versions of a disk without re-imaging and forcing administrators to use complex imaging tools.
Innovation Solution
A system with multiple mounting points on a common volume allows concurrent access by multiple client computers, enabling clients to boot from different versions of a disk and revert to saved modifications without re-imaging, using topmost overlays to store and manage different disk versions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual disks use traditional hard drive technology, then physical storage is reliable, but version control and reversibility are lost
Solution Approach 1:
The virtual disk is segmented into a base disk image and multiple overlay files, where each overlay represents a version or modification layer. This segmentation allows the system to maintain the original reliable storage while enabling version control through layered modifications that can be independently managed and reverted.
Solution Approach 2:
The patent implements a nested structure where overlay files are stacked on top of the base disk image, with each overlay containing modifications specific to a particular version. This nesting allows multiple versions to coexist within the same storage structure, enabling both reliability of the base image and adaptability for version control.
2Productivity
If data is written once to virtual disk, then storage efficiency is improved, but ability to return to previous state is lost
Solution Approach 1:
The system creates preliminary overlay files that contain modifications before they are permanently committed to the base disk image. These preliminary overlays act as save points, allowing users to revert to previous states without re-writing the entire disk, thus maintaining storage efficiency while enabling reversibility.
Solution Approach 2:
When a user needs to revert to a previous version, the system discards the current overlay and recovers a previous overlay or base image state. This mechanism allows efficient reversal without requiring complete data rewriting, preserving both storage efficiency and ease of operation.
3Adaptability or versatility
If multiple versions of disk are stored separately, then version control is enabled, but device complexity increases
Solution Approach 1:
Multiple disk versions are merged into a single unified structure consisting of a base image and stacked overlay files. This merging approach enables version control functionality while avoiding the complexity of managing completely separate disk images, as all versions share the common base and overlay structure.
Solution Approach 2:
The overlay structure serves multiple functions: it stores modifications, enables versioning, facilitates reverting to previous states, and allows concurrent access by multiple clients. This multi-functionality reduces the need for separate mechanisms, thereby reducing overall system complexity while enabling comprehensive version control.
4Adaptability or versatility
If re-imaging is used to provide different disk versions, then version control is achieved, but time consumption increases
Solution Approach 1:
The system counteracts the time-consuming re-imaging process by using differential overlays that only contain the differences between versions. Instead of rewriting the entire disk image, the system applies lightweight overlay files that represent only the changed portions, dramatically reducing the time required to provide different disk versions.
Solution Approach 2:
The version control system is made dynamic through the overlay mechanism, allowing versions to be created, modified, and switched without rigid re-imaging procedures. This dynamic approach enables rapid version changes by applying or removing overlay files rather than performing time-consuming complete re-imaging operations.
Data Source
AI summary
A system (10) for virtual disks version control includes a selectively read-only volume (12); at least one topmost overlay (141, 142, 143, 144, 145); and at least two intermediate, selectively read-only overlays (16, 16′, 16″, 16′″) configured as at least two mounting points. The at least one topmost overlay (141, 142, 143, 144, 145) is configured to store the results of redirected write operations. One of the at least two mounting points (16, 16′, 16″, 16′″) and the volume (12) form an image, and the other of the at least two mounting points (16, 16′, 16″, 16′″) and the volume (12) form another image. The at least two intermediate overlays (16, 16′, 16″, 16′″) are operatively located between the volume (12) and the at least one topmost overlay (141, 142, 143, 144, 145). Each of the at least two mounting points (16, 16′, 16″, 16′″) is configured to enable a plurality of client computers (18) to concurrently read the image or the other image and to concurrently write to a respective one of the at least one topmost overlays (141, 142, 143, 144, 145).