Virtual Extent Virtualization for Master-Image VHD Updates
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Solution Overview
Problem
Updating a master-image virtual hard disk (VHD) to apply software patches or service packs can result in space allocation collisions with existing differencing VHDs, either overwriting them or failing to update the master image, due to the lack of reserved space for updates.
Innovation Solution
Introducing an additional level of abstraction to extend the space allocated to the parent group, allowing for reserved blocks for updates without affecting dependent differencing VHDs, and merging metadata across groups to present a unified view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the master-image VHD space is expanded to apply updates, then the master image can be updated with patches and service packs, but existing differencing VHDs may be overwritten or space allocation collisions occur
Solution Approach 1:
The storage space is segmented into distinct allocations: original master-image VHD space, allocated differencing VHD space, and additional reserved space for updates. This segmentation prevents update operations from overwriting differencing VHDs by providing dedicated update space.
Solution Approach 2:
Space for updates is reserved in advance when the master-image VHD is created or when differencing VHDs are allocated. This preliminary allocation ensures that update space is available before updates are needed, preventing space allocation collisions during update operations.
2Quantity of substance
If differencing VHDs are allocated from the master-image VHD space, then storage utilization is improved, but no reserved space remains for master image updates
Solution Approach 1:
The total storage space is divided into separate allocated portions: space for the master-image VHD, space for differencing VHDs, and reserved space for updates. This segmentation allows the system to maintain high storage utilization while guaranteeing space availability for future update operations.
Solution Approach 2:
The update space is reserved in advance as part of the initial space allocation process. By performing this preliminary reservation, the system ensures that differencing VHDs can be allocated efficiently while maintaining the capability to update the master image without space conflicts.
3Quantity of substance
If the master image is updated without reserved space, then storage efficiency is maintained, but space allocation collisions occur during updates
Solution Approach 1:
Space for updates is reserved in advance during the initial allocation phase. This preliminary action ensures that when updates are needed, the space is already available and no reallocation or collision handling is required, maintaining both storage efficiency and ease of updating.
Solution Approach 2:
The storage space is segmented to include a dedicated reserved portion for updates. This segmentation allows the system to maintain efficient storage utilization while providing a guaranteed space for update operations, eliminating the need for complex space management during updates.
Data Source
AI summary
Files can be segmented into distinct groups and allocated storage units such as blocks. Files associated with parent and child files can be segmented into separate groups, for instance. Further, a group associated with parent files can be extended to include additional blocks reserved for subsequent update. Additionally, metadata can be merged across groups to provide a unified view of the distinct groups.