Red Hat SummitChapter 1. About the Migration Toolkit for Virtualization
You can migrate virtual machines from VMware vSphere, Red Hat Virtualization, or OpenStack source providers to OpenShift Virtualization with the Migration Toolkit for Virtualization (MTV).
Migration using OpenStack source providers is a Technology Preview.
Migration using OpenStack source providers is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.
Migration using OpenStack source providers only supports VMs that use only Cinder volumes.
Additional resources
1.1. About cold and warm migration
MTV supports cold migration from Red Hat Virtualization (RHV) and warm migration from VMware vSphere and from RHV.
As a Technology Preview, MTV supports cold migration using OpenStack source providers.
Migration using OpenStack source providers is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.
For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.
Migration using OpenStack source providers only supports VMs that use only Cinder volumes.
1.1.1. Cold migration
Cold migration is the default migration type. The source virtual machines are shut down while the data is copied.
1.1.2. Warm migration
Most of the data is copied during the precopy stage while the source virtual machines (VMs) are running.
Then the VMs are shut down and the remaining data is copied during the cutover stage.
Precopy stage
The VMs are not shut down during the precopy stage.
The VM disks are copied incrementally using changed block tracking (CBT) snapshots. The snapshots are created at one-hour intervals by default. You can change the snapshot interval by updating the forklift-controller deployment.
You must enable CBT for each source VM and each VM disk.
A VM can support up to 28 CBT snapshots. If the source VM has too many CBT snapshots and the Migration Controller service is not able to create a new snapshot, warm migration might fail. The Migration Controller service deletes each snapshot when the snapshot is no longer required.
The precopy stage runs until the cutover stage is started manually or is scheduled to start.
Cutover stage
The VMs are shut down during the cutover stage and the remaining data is migrated. Data stored in RAM is not migrated.
You can start the cutover stage manually by using the MTV console or you can schedule a cutover time in the Migration manifest.
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