Red Hat OpenStack VMware Migration toolkit deep-dive

When an organization currently on VMware evaluates transitioning to a new cloud platform, such as Red Hat OpenStack Services on OpenShift, a key initial concern is typically the effective migration of VMware virtual machine workloads. The Red Hat OpenStack VMware Migration toolkit specifically addresses this need, providing an Ansible collection that aims to simplify and automate the migration process from VMware environments into Red Hat OpenStack Services on OpenShift. This toolkit significantly reduces the complexity and downtime often associated with manual migrations, enabling organizations to rapidly and smoothly adopt cloud-native architectures.

This article provides a deep dive into migrating VMware-based workloads to Red Hat OpenStack Services on OpenShift. By following this guide, you’ll gain the essential knowledge and tools needed to plan and execute a successful, efficient migration.

Highlights

The Red Hat OpenStack VMware Migration Toolkit, delivered as an Ansible collection, comes with a powerful set of features designed to streamline and scale your migration efforts:

• Discovery mode: automatically gathers metadata from VMware vCenter, including VM definitions, network configurations, and storage details.
• Network mapping: supports mapping of source networks and ports to target Red Hat OpenStack Services on OpenShift networks, including MAC address preservation.
• Flavor mapping and flavor creation: enables mapping VMware hardware profiles to OpenStack flavors or dynamically creates matching flavors during migration.
• Warm VM migration support: migrates running virtual machines with minimal disruption by leveraging snapshot and CBT-based mechanisms.
• Multi-disk and multi-NIC support: fully supports virtual machines with complex storage and networking setups, ensuring consistent and complete migration.
• Operating system compatibility: supports a broad range of guest OSes compatible with virt-v2v and certified for use with Red Hat OpenStack Services on OpenShift.

Ansible Integration with Ansible Automation Platform

One of the key advantages of the Red Hat OpenStack VMware Migration toolkit is its deep integration with Ansible, making it a natural fit for organizations using Ansible Automation Platform (AAP).

• Automation: the migration process is fully automated using Ansible playbooks, reducing manual intervention and ensuring consistency.
• Scalability: Ansible Automation Platform allows migration at scale by orchestrating multiple migration tasks simultaneously.
• Extensibility: existing Ansible modules can be extended or modified to meet specific enterprise needs, such as pre-migration validation, post-migration testing, and custom workflows.

OpenStack APIs and Changed Block Tracking (CBT) for Warm Migration

Achieving warm migration requires a method that minimizes downtime while ensuring data consistency. The Red Hat OpenStack VMware Migration toolkit leverages:

• OpenStack APIs: Native OpenStack APIs are used to provision, manage, and migrate VMs, ensuring a smooth transition to Red Hat OpenStack Services on OpenShift.
• Changed Block Tracking (CBT)-Enabled Incremental Sync: CBT allows tracking changes at the block level, enabling efficient and fast incremental data synchronization.
• Minimal Downtime: Instead of performing a full data copy at once, Changed Block Tracking (CBT) ensures that only changed blocks are transferred, reducing network and storage overhead.

Infrastructure Components in the Migration Process

vCenter Source Hypervisor

The VMware vCenter environment acts as the source hypervisor, hosting the virtual machines to be migrated.

vCenter provides VM management, snapshot capabilities, and Change Block Tracking (CBT) data used for incremental synchronization.

Red Hat OpenStack Services on OpenShift Target Cloud

OpenStack Services on OpenShift serves as the destination cloud platform, where migrated virtual machines will be recreated and managed.

It leverages OpenStack-native services such as Cinder for storage, Nova for compute, and Neutron for networking to ensure seamless VM operation post-migration.

Ansible Automation Platform

The Migrator Host is responsible for running the Ansible collection that orchestrates the migration. It can be a standalone external host using the ansible-playbook CLI or an Ansible job execution using Ansible Automation Platform (AAP). Using AAP provides centralized management, workflow automation, and seamless integration with enterprise CI/CD pipelines, making large-scale migrations more efficient and maintainable.

Conversion Host

To transfer virtual machine data efficiently, the migration process utilizes a specialized virtual machine known as the Conversion Host, which is deployed in the Red Hat OpenStack Services on OpenShift environment. Instead of routing VM and volume data through the Migrator Host, the Conversion Host allows direct transfer from the VMware environment to Red Hat OpenStack Services on OpenShift. This approach optimizes network bandwidth, improves performance, and significantly accelerates the migration process while reducing unnecessary resource consumption.

Migration Workflow Overview

1. Deploy the Conversion Host
   • Set up a RHEL-based conversion host manually or allow the Red Hat OpenStack VMware Migration toolkit to deploy it automatically in the target Red Hat OpenStack Services on OpenShift environment..
2. Configure Authentication
   • Define Ansible variables for vCenter and Red Hat OpenStack Services on OpenShift authentication credentials.
3. Define Migration Parameters
   • Specify the list of virtual machines (VMs) to migrate and any additional parameters in Ansible variables.
4. Initiate the Migration
   • Execute the migration playbook to start the process.
5. Gather VM Information
   • The Red Hat OpenStack VMware Migration toolkit collects VM metadata, including configuration details and disk information.
6. Create and Attach Cinder Volume
   • A Cinder volume is provisioned and attached to the conversion host.
   • A snapshot of the VM’s disks is created in the source VMware environment.
7. Changed Block Tracking (CBT)-Based Disk Transfer
   • The virtual machine disk is copied through the conversion host to the Cinder volume.
   • The Red Hat OpenStack VMware Migration toolkit retrieves the CBT ID from the VMware guest and assigns it to the volume metadata.
   • Example: in the following diagram the initial CBT ID is 52 05 1c 73_/386.

8. Incremental Sync of Divergent Blocks
   • Before converting the volume and creating the OpenStack instance, the Red Hat OpenStack VMware Migration toolkit verifies whether the CBT ID has changed.
   • Example: If the new CBT ID is 99 04 1c 73_/561, the Red Hat OpenStack VMware Migration toolkit identifies the divergent blocks and synchronizes only the modified data (99 04 1c 73_/561). This ensures that only the incremental changes are applied, reducing network and storage overhead.
   • Once the sync is complete, the VMware snapshot is deleted to finalize the data transfer.
9. Finalizing the Migration and VM Creation
   • The virtual machine is created in OpenStack, configured using the gathered metadata, and the just-synced Cinder volume is attached to the target VM.
   • The VM is then started in the Red Hat OpenStack Services on OpenShift environment with minimal downtime.

By leveraging Changed Block Tracking (CBT), this approach significantly reduces migration time, optimizes resource utilization, and minimizes service disruption for running workloads.

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