Virtual Machine Live Migration Rollback via Dirty Page Copying
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Solution Overview
Problem
Conventional live migration of virtual machines in cloud computing faces challenges such as incomplete memory transfer during delayed-copy migration, leading to inability to roll back to the source physical machine in case of failures like network interruptions or destination machine faults, resulting in the virtual machine being unable to run independently on either machine.
Innovation Solution
Implementing a method where the destination physical machine copies dirty memory pages to the source physical machine upon failure, and the source physical machine updates and stores these pages, allowing the virtual machine to roll back and run independently on the source machine by maintaining complete and latest memory pages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If delayed-copy migration is used to reduce migration time, then migration speed is improved, but system reliability deteriorates because the virtual machine cannot roll back upon failure
Solution Approach 1:
The patent applies preliminary action by pre-copying memory pages from source to destination before the actual migration execution. This allows the destination to have most memory pages ready, enabling fast migration while maintaining rollback capability through the dirty page tracking mechanism that identifies which pages need final synchronization.
Solution Approach 2:
The patent implements feedback through dirty page tracking and notification mechanisms. When migration fails, the system receives feedback about the failure state and uses tracked dirty page information to determine which pages need to be copied back to the source, enabling reliable rollback while maintaining fast migration performance.
2Manufacturing precision
If multiple rounds of recursive memory copying is performed to ensure complete memory transfer, then memory transfer completeness is improved, but migration time increases
Solution Approach 1:
The patent applies partial action by copying only the necessary memory pages rather than performing complete multiple-round recursive copying. The dirty page tracking mechanism identifies exactly which pages were modified and need to be transferred, eliminating redundant copying operations while ensuring complete memory state transfer.
Solution Approach 2:
The patent changes the parameter of memory copying from iterative complete copying to selective dirty page copying. By tracking which pages are dirty (modified) during migration, the system transfers only those specific pages that need updating, reducing total copying time while maintaining completeness.
3Productivity
If the virtual machine is executed on the destination machine during migration, then migration continuity is improved, but the ability to roll back upon failure deteriorates
Solution Approach 1:
The patent uses dirty page tables and notification mechanisms as intermediaries between the running virtual machine and the migration rollback process. These intermediaries track memory modifications and enable the source machine to reconstruct the complete memory state even after the VM has started executing on the destination, maintaining both continuity and rollback capability.
Solution Approach 2:
The patent employs copying of dirty memory pages from destination back to source upon failure detection. This copying mechanism ensures that the source machine receives the updated memory pages, allowing it to restore the virtual machine with complete and accurate memory state, thereby maintaining rollback capability while the VM was running on destination.
Data Source
AI summary
Systems and methods for live migration of a virtual machine are provided. The methods include: copying, by a destination physical machine according to a recorded dirty page table, dirty memory pages corresponding to dirty memory page identifiers in the dirty page table to a source physical machine when live migration of a virtual machine fails in a delayed-copy mode, and updating and storing, by the source physical machine, the copied dirty memory pages. When live migration of a virtual machine fails, dirty memory pages corresponding to dirty memory page identifiers in a dirty page table are copied to a source physical machine to be updated and stored, so that the source physical machine has complete and the latest memory pages, and the virtual machine can roll back to and run independently on the source physical machine.