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Instance Maintenance: Live/Offline Migration and Reboots

Understanding Live Migration

Live migration is the process of moving a virtual machine (VM) from one physical server to another while keeping it operational. This allows us to perform infrastructure updates and maintenance without service disruption.

Why is Live Migration Necessary?

Live migration is essential for maintaining a stable and high-performing cloud environment. It is typically used for:

  • Infrastructure Maintenance: Performing updates and security patches on physical servers without downtime.
  • Load Balancing: Redistributing workloads to optimize performance and resource usage.
  • Hardware Upgrades: Transitioning instances to new hardware seamlessly.
  • Proactive Issue Resolution: Moving instances away from potentially failing hardware to prevent outages.

How Does Live Migration Work?

  1. Duplication: The system copies the VM’s memory and state to a new host.
  2. Synchronization: Changes made during the transfer are continuously updated.
  3. Switchover: The VM pauses momentarily before resuming on the new server.
  4. Completion: Final processes ensure the instance operates normally on the new host.

Live migration minimizes downtime and ensures a flexible and reliable cloud infrastructure.

Understanding Reboots and Offline Migrations

While live migration is the preferred method for maintaining cloud instances, there are scenarios where a full power cycle (shutting down and restarting an instance) or an offline migration is necessary.

Why is a Full Power Cycle Sometimes Required?

In some cases, simply rebooting an instance is not sufficient. Instead, it must be completely powered off and restarted. This may be necessary for:

  • Hypervisor Updates: Some security patches or new hypervisor features require a full shutdown and restart to apply properly.
  • Virtual Machine Configuration Changes: Certain virtual machine settings (like CPU configurations) can not be changed while the instance is booted and require a full shutdown and a restart to take effect.

Why is an Offline Migration Necessary?

Offline migration moves an instance to a new physical server by shutting it down first, unlike live migration, which occurs with minimal downtime. This is required when:

  • Incompatible Configurations: Some workloads with specific hardware dependencies cannot be migrated live.
  • Fault Recovery: When a hardware failure already occurred, instances must be moved to a healthy host.

What to Expect

  • Full Power Cycle (Shutdown and Restart Required by Customer):
    In certain cases, a simple reboot is not enough. Customers are required to fully power off and restart their virtual machine to apply necessary updates and maintain system stability.

  • Enforced Shutdown by Cloud Team (If Not Completed by Customer):
    If the required shutdown and restart are not performed within the communicated time frame, our cloud operations team will proactively power off and restart the instance to ensure system integrity by the due date. This could result in an unexpected interruption.

  • Offline Migration:
    If an instance needs to be offline migrated to a different physical host, the system will be powered off, migrated, and then restarted. This action is completely done by the cloud team. Customers will be informed in advance about any necessary actions.

Commitment to Reliability

Our team ensures that all maintenance activities are handled efficiently to maintain a secure and reliable cloud environment.