VM migration lifecycle

This page describes the phases a particular VM undergoes during a migration to GCP. Some phases are optional, and others are unavailable during cloud-to-cloud migrations.

Test clone

A test clone creates clones of selected VMs to test them in Google Cloud Platform (GCP). The test clone behaves like the live systems and leverages data from the source VM. However, test clones do not modify any live data because data from the test environment is not written back on-premises. Upon creating a test clone, Migrate for Compute Engine:

  1. Attaches to the VM volumes.
  2. Starts each instance in GCP. Storage is streamed from the VM to GCP.

For more information about how to use test clones, see Testing migrated workloads.

Delete clone

Deleting the test clone removes it from GCP.

Note that deleting the test clone has no impact whatsoever on your live system or data. Any changes made to data in the test clone are not replicated back to your live system.


This operation moves the source VMs from your on-premises data center to GCP. This does not completely move VM storage to the cloud.

The run-in-cloud operation:

  1. Shuts down the source VMs.
  2. Attaches to the VM's volumes.
  3. Starts the VM on GCP, streaming storage as needed.

Move back

Moves the instances in GCP back to their source, either on-premises or AWS.

The move-back operation:

  1. Stops the VMs.
  2. Moves storage back to source.
  3. Deletes the GCP instances.

Full migration

The full migration operation moves VMs in one step from source to target. In doing so, it:

  1. Performs the run-in-cloud process described above.
  2. Waits for the VMs to be in the Cache on Demand state, when storage is streamed to the cloud.
  3. Migrates the VM data to GCP.
  4. After storage is fully copied to GCP, prepares the VM to detach from GCP.

When this process has completed, the VM state changes to Ready to Detach.

Offline migration

Migrate for Compute Engine can migrate workloads with operating systems or file systems that Migrate for Compute Engine's streaming technology does not support, but that the cloud environment does support.

During the offline migration process, Migrate for Compute Engine:

  1. Migrates storage.
  2. Starts the new VM only after migration is completed.
  3. Detaches the VM.

Prepare to detach

This operation takes VM disks from the Migrate for Compute Engine cache and object store and creates the native data drives in GCP. After this operation finishes, you can detach the VM from the Migrate for Compute Engine cache.


In the detach sequence, Migrate for Compute Engine:

  • Shuts down the VM in the cloud.
  • Performs any final data synchronization necessary.
  • Attaches the native disks to the instance.
  • Starts the instance in GCP.


After the VMs are detached and you have completed any required validation, you can start the detach cleanup. Each VM is then marked as unmanaged by Migrate for Compute Engine.



Migrate for Compute Engine (formerly Velostrata)