How vMotion Works in Vmware


How vMotion Works in Vmware

vMotion is a feature in VMware virtualization technology that allows you to move a running virtual machine from one physical server to another without any interruption to the service. This capability is helpful for tasks like hardware maintenance, load balancing, or moving virtual machines to different servers for better resource utilization.

To successfully perform a vMotion, IT managers must first ensure that several procedures are followed for a smooth migration. This includes configuring the network interfaces on both the source and target machines properly. Additionally, a substantial amount of bandwidth is required for the migration to be completed successfully.

Many IT experts recommend having an extra network interface controller ready for failover scenarios. Using jumbo Ethernet frames can also help ensure uninterrupted data migration.

Once the source and target servers are correctly set up, the migration process can begin. Below is a detailed explanation of the three technologies that enable VMware’s vMotion.

How vMotion Works in the background.

1. Pre-Migration Phase:

  • Compatibility Checks: Before initiating vMotion, vCenter Server ensures compatibility between source and destination hosts, including processor compatibility and shared storage accessibility.
  • Shared Storage Prerequisite: Both source and destination hosts must have access to shared storage where VM files and configurations reside. This ensures that VM data remains accessible during migration.

2. Memory Transfer:

  • Initial Copy: vMotion starts by copying the VM’s memory contents from the source host to the destination host over the vMotion network. This involves sending an initial “snapshot” of the VM’s memory.
  • Iterative Synchronization: While the initial copy is underway, vMotion continuously tracks and synchronizes any changes made to the VM’s memory. Multiple iterations occur until the two hosts are nearly in sync.

3. vMotion Switchover:

  • ¬†Pause and Final Synchronization: Once the bulk of the VM’s memory has been transferred, a momentary pause is introduced to finalize the remaining changes to memory. This ensures consistency between the source and destination.
  • Network Switch: During the pause, there’s a network switch. Incoming and outgoing network traffic is redirected to the destination host, preparing for the VM to resume operation on the new host.

4. Completion and Post-Migration:

  • Seamless Transition: The VM is now running on the destination host, and users experience no disruption. This transition is transparent to end-users and applications.
  • Resource Cleanup: After the successful migration, the resources on the source host are released, and the VM’s configuration is updated to reflect its new location.

5. Network Handling:

  • MAC Address Preservation: To avoid network disruptions, vMotion ensures the VM retains its original MAC address. This preservation occurs during the switchover to maintain network identity.
  • ¬†Switching Connectivity: The network switch redirects incoming and outgoing network traffic from the source to the destination host, ensuring uninterrupted communication with the VM.

6. Continuous Monitoring:

  • Post-Migration Checks: vCenter Server continuously monitors the migrated VM on the destination host, ensuring its stability and performance.
  • Rollback Mechanism: If any issues are detected during or after migration, vMotion includes a rollback mechanism to revert the VM to its original state on the source host.
Source: VmwareFirewall Rules for vMotion
Source: Vmware
Firewall Rules for vMotion

VMware Mastery

Hi, I've been working with Windows, VMware and Cloud technologies for more than 12 years. I love delving into the exciting realm of technology and enjoy sharing my knowledge with others. I write about IT and Technology, covering both technical and non-technical topics.

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