VM Migration Caching Disablement for Reliability

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Solution Overview

Problem

Live migration of virtual machines (VMs) often fails due to ongoing disk I/O operations during the migration process, as the VM's in-memory cache is rewritten, leading to performance issues and potential failure.

Innovation Solution

Disabling in-memory caching of the VM during migration and zeroing out cache pages to prevent their transfer, allowing for quicker convergence and completion of the migration process by slowing down disk writes and reads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If in-memory caching is enabled during VM migration, then disk I/O performance is improved, but migration reliability deteriorates due to cache rewriting

Engineering Contradiction:

Improvedisk I/O performanceVSAvoidmigration reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by disabling the in-memory cache before the migration process begins and clearing any cached data. This preparatory step ensures that no cache rewriting occurs during migration, thereby preventing migration failures while maintaining acceptable disk I/O performance through the use of page cache tracking and selective data transfer.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If in-memory caching is disabled during VM migration, then migration reliability is improved, but disk I/O performance deteriorates

Engineering Contradiction:

Improvemigration reliabilityVSAvoiddisk I/O performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent extracts the problematic in-memory cache component from the migration process by disabling it specifically during migration operations. This allows the migration to proceed reliably without cache interference, while the system can still utilize page cache tracking to maintain efficient data transfer by identifying and transferring only the necessary pages.

Inventive Principle:

Principle #2Taking out (Extraction)

3Stability of the object's composition

If cache pages are transferred during migration, then data consistency is maintained, but migration time increases

Engineering Contradiction:

Improvedata consistencyVSAvoidmigration time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The patent uses copying by tracking which pages have been modified (dirty pages) during migration and transferring only those specific pages to the destination host. This selective copying approach maintains data consistency for the migrated VM while significantly reducing the total amount of data transferred compared to transferring the entire cache, thereby reducing migration time.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS10635477B2Disabling in-memory caching of a virtual machine during migration

Publication Date: 2020.04.28 RED HAT ISRAEL

AI summary

Systems and methods for disabling in-memory caching of a virtual machine during migration are disclosed. An example method may include receiving, at a migration agent of a source host machine, a request to migrate a virtual machine (VM) hosted by the source host machine to a destination host machine, determining that a migration caching attribute of the VM is enabled, instructing a VM agent executing on the VM to disable caching of the VM in view of determining that the migration caching attribute of the VM is enabled, receiving acknowledgment of successful disablement of caching on the VM, and responsive to receiving the acknowledgment, initiating migration of the VM from the source host machine to the destination host machine.