Pre-warming Virtual Machine Memory for Live Migration
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Solution Overview
Problem
Conventional live migration of virtual machines between hosts results in significant downtime due to the need for suspending the source virtual machine during the migration process, which is impractical for large systems and prone to network-related failures.
Innovation Solution
Implementing a pre-warm-up migration phase where the source migration manager continuously copies data segments of the virtual machine to the destination host, even after the entire state has been copied, until a warm-up exit condition is met, allowing for seamless transition and reducing downtime, and enabling concurrent migration to multiple hosts to minimize failure chances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source virtual machine is suspended during migration to copy its state, then the migration can be completed, but the downtime increases significantly
Solution Approach 1:
The patent applies preliminary action by continuously copying memory pages from the source host to the destination host before the actual migration is needed. The pre-warmup phase proactively transfers pages in advance, so that when migration is triggered, most pages are already available at the destination, significantly reducing the downtime required for the stop-and-copy phase.
Solution Approach 2:
The patent implements continuity of useful action by maintaining continuous copying of memory pages during the pre-warmup phase, even while the virtual machine remains running. This continuous background copying ensures that pages are transferred incrementally over time, allowing the migration process to progress without interrupting the virtual machine's operation.
2Loss of time
If the source virtual machine continues running during migration, then downtime is reduced, but the complexity of the migration process increases
Solution Approach 1:
The patent employs feedback mechanisms to monitor the migration process while the virtual machine continues running. The system tracks which memory pages have been copied, identifies dirty pages that need re-copying, and dynamically adjusts the copying process based on the current state. This feedback loop enables the complex coordination required for live migration without manual intervention.
Solution Approach 2:
The patent introduces intermediary components including a migration manager and page fault handlers that mediate between the running source virtual machine and the destination host. These intermediaries manage the complex interactions, coordinate page transfers, and handle page faults, thereby organizing the complexity into manageable subsystems.
3Loss of time
If memory pages are continuously copied during the pre-warmup phase, then the down-time is reduced, but the network bandwidth consumption increases
Solution Approach 1:
The patent applies partial action by copying only the necessary memory pages during the pre-warmup phase rather than all pages. The system identifies and copies pages that are actually needed for the virtual machine's operation, leaving unnecessary pages to be transferred later during the stop-and-copy phase. This selective copying reduces network bandwidth consumption while still achieving the goal of minimizing downtime.
Data Source
AI summary
A method for fast migrating of a source virtual machine located on a source host to one or more destination hosts is provided. A source migration manager of a hypervisor receives identities of a plurality of destination hosts. The source migration manager copies at least one data segment corresponding to a portion of a state of a source virtual machine to the pluralities of destination hosts. The source migration manager receives a command to migrate the source virtual machine to one or more selected destination hosts of the plurality of destination hosts after copying the at least one data segment to the destination hosts. When the source migration manager receives an indication of successful booting of at least one destination virtual machine, the source migration manager terminates transmission of the state of the source virtual machine to the remaining plurality of destination hosts.