Virtualization Manager Snapshot Coordination for Shared Disk VMs

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Solution Overview

Problem

Taking a snapshot of a shared disk among multiple virtual machines can cause disruptions to their operations due to pending input and output activities.

Innovation Solution

A mechanism is implemented where a manager suspends operations and flushes pending IO activities of the virtual machines before taking a snapshot, creating a new active snapshot VM image while the original image serves as a backup copy, allowing the VMs to resume operations using the new image.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a snapshot is taken of a shared disk among multiple virtual machines, then a backup copy of the VM image is created, but disruptions occur to the operations of the VMs due to pending input and output activities

Engineering Contradiction:

Improvesnapshot creation reliabilityVSAvoidVM operations continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs preliminary actions by suspending I/O activities and flushing pending operations to stable storage before creating the snapshot. This ensures data consistency for the snapshot while minimizing disruption to VM operations, as the suspension is temporary and only affects the snapshot creation moment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system introduces an intermediary mechanism (snapshot manager) that coordinates between multiple VMs sharing the same disk. This intermediary manages the snapshot process by controlling I/O suspension, coordinating the snapshot creation, and orchestrating the resumption of operations, thereby resolving the conflict between snapshot reliability and VM continuity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If I/O activities are suspended to ensure consistent snapshot data, then snapshot accuracy is improved, but VM operations are halted

Engineering Contradiction:

Improvesnapshot data consistencyVSAvoidVM operation interruption time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The system flushes pending I/O activities to stable storage before suspending I/O operations. This preliminary action ensures that all data is already written and stable when the snapshot is taken, guaranteeing data consistency without needing to maintain suspension for extended periods, thus minimizing operational interruption time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system rapidly performs the snapshot creation process once I/O activities are suspended, minimizing the duration of the suspension. By rushing through the snapshot capture and immediately resuming I/O operations, the system achieves data consistency while reducing the time VM operations are halted to the absolute minimum necessary.

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS8930652B2Method for obtaining a snapshot image of a disk shared by multiple virtual machines

Publication Date: 2015.01.06 RED HAT ISRAEL

AI summary

Methods for obtaining a snapshot of a shared virtual machine (VM) image are described herein. In response to a request for obtaining a snapshot of a first VM image stored in a storage disk accessed and shared by a plurality of VMs, a virtualization manager selects a VM from the plurality of VMs hosted within one or more hosts. First needs to notify others to prepare for the snapshot by pausing, etc. A process associated with the selected VM is configured to capture a snapshot from the first VM image, generating a second VM image to be stored in storage disk. Thereafter, the virtualization manager notifies the plurality of VMs to utilize the second image after the second VM image has been generated.