Virtual Machine Migration Triangle Approach
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Solution Overview
Problem
The migration of virtual computer systems across host computer systems is often time-consuming and disruptive, especially for large or complex systems, leading to restricted user interaction and potential operational issues due to volatile system resources like attached storage and network connections.
Innovation Solution
A phased approach to virtual machine migration that manages access to block storage devices, using a triangle method to ensure correct ordering of input-output requests and lock resources during the critical migration phase, maintaining state consistency between the source and target virtual machine instances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the virtual computer system is halted and memory/system state is copied to migrate it to a different host computer system, then the migration can be completed, but the migration process takes a significant amount of time and user interaction is eliminated or severely restricted
Solution Approach 1:
The patent applies preliminary action by copying the virtual computer system's memory and system state to the target host computer system before halting the source system. This allows the target system to be prepared in advance, and when the migration is executed, the actual transition is much faster because the heavy lifting of data copying has already been done. The system state is captured and transferred preliminarily, minimizing the downtime during the actual migration switch.
2Adaptability or versatility
If the virtual computer system is migrated by copying memory and system state, then the system can be moved to a different host, but attached storage and network connections may be volatile, introducing the possibility that the migrated system differs significantly from the original
Solution Approach 1:
The patent uses an intermediary approach by introducing a state capture and transfer mechanism that acts as a mediator between the source and target systems. The system state is captured from the source, transferred through a controlled intermediary process, and then applied to the target system. This intermediary process ensures that storage and network connections are properly handled and synchronized, maintaining system state consistency across the migration.
Solution Approach 2:
The patent implements feedback mechanisms to verify that the migrated virtual computer system matches the original system state. After copying the memory and system state to the target host, the system performs verification checks to ensure consistency. If discrepancies are detected in the migrated system compared to the original, corrective actions are taken to restore fidelity, ensuring that the migrated system is an accurate replica.
3Ease of manufacture
If the virtual computer system is halted for migration, then the migration process can proceed, but the ability of a user to interact with the virtual computer system during that time period is eliminated or at least severely restricted
Solution Approach 1:
The patent applies preliminary action by performing the migration preparation and state copying while the system is still running and accessible to users. The actual halting and switching is minimized to a brief moment after the preliminary work is complete. This allows users to continue interacting with the system during the preparation phase, and only experience brief interruption during the final switch, significantly improving ease of operation.
Data Source
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AI summary
Techniques for preserving the state of virtual machine instances during a migration from a source location to a target location are described herein. A set of credentials configured to provide access to a storage device by a virtual machine instance at the source location is provided to the virtual machine instance. When the migration from the source location to the target location starts, a second set of credentials configured to provide access to a storage device by a virtual machine instance at the source location is provided to the virtual machine instance. During the migration, a response to an input-output request is provided to one or more of the locations using the set of credentials and based at least in part on the state of the migration.