Auxiliary Overlay for Write Filter Threshold Management
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Solution Overview
Problem
Current write filter technologies face challenges with volatile and persistent overlays, including consumption thresholds leading to reboot issues, inability to register exclusions, and limitations in features like Hibernate Once, Resume Many (HORM), which affect system performance and data preservation across reboots.
Innovation Solution
An overlay optimizer is employed to manage I/O requests and selectively move artifacts to an auxiliary overlay, allowing for a HORM-like experience without enabling the write filter's HORM feature, by configuring a list of monitored artifacts or excluded applications, and managing the auxiliary overlay's persistence or volatility based on the write filter's state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a volatile overlay is used with write filter to prevent modifications to protected volume, then the protected volume maintains its original state across reboots, but the overlay consumption reaches critical threshold leading to forced reboots and loss of cached artifacts
Solution Approach 1:
The patent divides the overlay storage into two separate overlays: a first overlay for caching artifacts from the protected volume, and a second overlay for caching artifacts from the visible volume. This segmentation allows independent management of each overlay's consumption, preventing the critical threshold issue that occurs when all artifacts are cached in a single volatile overlay.
Solution Approach 2:
The patent introduces a visible volume as an intermediary layer between the protected volume and the second overlay. Artifacts are first cached in the visible volume, then selectively moved to the second overlay based on consumption thresholds. This intermediary mechanism allows controlled data transfer and prevents unbounded growth of overlay consumption.
2Duration of action of stationary object
If a persistent overlay is used with write filter to maintain artifacts across reboots, then artifacts are preserved across system restarts, but the overlay quickly exceeds critical threshold causing indefinite reboots
Solution Approach 1:
The patent implements dynamic management of the second overlay by selectively moving artifacts between the visible volume and the second overlay based on consumption thresholds. This dynamic adjustment allows the system to adapt to changing storage conditions and prevent the persistent overlay from exceeding critical thresholds that would cause indefinite reboots.
Solution Approach 2:
The patent changes the persistence parameter of the second overlay to be volatile rather than persistent, while maintaining artifact persistence through selective copying to the visible volume. This parameter change allows the overlay to be cleared on reboot without causing system instability, while the visible volume maintains the necessary artifact persistence.
3Duration of action of stationary object
If write filter HORM feature is enabled to preserve application state across reboots, then application state is maintained, but exclusions cannot be registered and system performance degrades
Solution Approach 1:
The patent segments artifact caching into two independent overlays with different persistence characteristics. The first overlay handles protected volume artifacts with volatile persistence, while the second overlay handles visible volume artifacts with selective persistence. This segmentation allows exclusion registration without the limitations of the HORM feature.
Solution Approach 2:
The visible volume serves as an intermediary that enables exclusion registration and selective artifact persistence. By moving artifacts through the visible volume before caching them in the second overlay, the system gains the ability to register exclusions and control which artifacts are persisted, avoiding the performance degradation and operational limitations of HORM.
4Reliability
If all artifacts are cached in a single overlay to maximize protection, then complete artifact preservation is achieved, but overlay consumption reaches critical threshold more quickly
Solution Approach 1:
The patent divides artifact caching across two separate overlays, each with its own consumption threshold management. This segmentation distributes the storage burden and allows independent threshold management, preventing the single overlay from reaching critical consumption levels that would force system reboots or artifact loss.
Solution Approach 2:
The visible volume acts as an intermediary storage layer that receives artifacts from the first overlay before they are moved to the second overlay. This intermediary mechanism allows controlled distribution of artifacts across multiple storage locations, managing overall consumption volume while maintaining complete artifact preservation.
Data Source
AI summary
An overlay optimizer can enhance the functionality of a write filter using an auxiliary overlay. An overlay optimizer can be loaded above a write filter. Based on the configuration of the write filter's overlay, the overlay optimizer can be configured to implement a volatile or persistent auxiliary overlay and then use the auxiliary overlay to selectively cache artifacts. To minimize the likelihood that the consumption of the write filter's overlay will exceed a critical threshold, the overly optimizer can be provided a list of monitored artifacts. The overlay optimizer can employ the list to selectively move monitored artifacts from the write filter's overlay to the auxiliary overlay when the overlay's consumption reaches a threshold. The overlay optimizer may also selectively allow I/O requests generated by particular applications while redirecting I/O requests generated by other applications.