Migrate VS from Xen to KVM

KVM virtualization becomes more and more popular nowadays due to the number of reasons. With KVM, you get faster and more reliable technology together with more functionality in cloud operation. Because of that, OnApp has chosen to move forward with KVM, migrating current virtual servers running on Xen to KVM compute resources.

This feature allows to perform migration of virtual servers hosted on Xen compute resources to KVM compute resources. Migration to KVM is easy and requires few steps before converting Xen virtual servers to KVM. During the migration process, you only need to choose a target compute resource and data store. Additionally, you can enable a backup before or after the migration. You can initiate the migration using the procedure described in this document.  

On this page:

Before You Begin

Before you proceed further, please note that:

  • The migration process is straightforward and should succeed on most virtual servers. However, in some cases something might go wrong. OnApp provides several measures to prevent data loss. You can Clone the VS before migration or you can enable the additional backup option in the migration wizard that would allow to convert the backup to a template.
  • Migration is irreversible and you cannot migrate from KVM to Xen compute resources.
  • During the migration, the billing will be changed due to the increase of disk size (all disks except swap disks increase in size by 1 GB). The new estimated price per hour for a VS is displayed at the bottom of the VS migration screen.
  • Migration is not performed if a virtual server has temporary disks (attached to or from other virtual server).

  • Migration is not performed for Integrated Storage data stores if any of the disks has active backups running or zobmie snapshots. Also, migration is not supported on SolidFire data stores.

  • Migration is not applicable for federated virtual servers that are built in compute zones submitted to the Marketplace.

  • This option is only available for Linux based VSs running on Xen compute resources. 
  • Check if your Linux template supports hot migration at the Linux Templates.
  • Destination compute resources should be running Centos 7. You must migrate or update your Centos 6 compute resources first.
  • If both source and destination compute resources have backup IP addresses, VS migration will be performed using those backup IP addresses as an alternative network for traffic. It is recommended to use alternative network not to load management network.
  • Networks attached to a VS running on Xen compute resource should be attached to KVM compute resources too.
  • Make sure your target data stores have enough space and are added to the target data store zone in your bucket. 
  • If you have TRIM enabled for at least one target data store before the migration, it can be enabled after the migration with the next VS reboot. 

Migrate Linux Virtual Server to KVM

Go to Admin > Settings Configuration Defaults > Migration options, if you want to set limit of transactions number which can be run simultaneously on the target compute resource when migrating a VS.

To migrate Linux VS from Xen to KVM, do the following:

  1. Go to your Control PanelCloud Virtual Servers.
  2. Click a label of a virtual server that you want to migrate.
  3. Click the Tools button and click the Migrate Virtual Server button.
  4. In the Migration Type box, select Xen to KVM Migrate and click Next.

Compute Resources

The first step enables you to select a compute zone and a resource to migrate your virtual server to. 

  • Target compute zone - select a destination compute zone
  • Target compute resource - select a destination compute resource

Click Next to select storage resources for the migration.

Storage Resources

At this step, you can specify target data stores running on the compute resource that you indicated previously:

  • Target data store for disk - select a destination data store for each disk. The list includes available data stores associated with the compute zone and compute resource that you selected earlier.

Click Next to select additional backup settings before or after migration.


Backups created while the VSs were running on Xen compute resources are incompatible with KVM. You may choose to keep them after migration, but they will not be available for recovery. However, such backups might be used to convert to templates.

Select the backups you will need before or after the migration from Xen to KVM is completed:

  • Schedule a backup before the migration - leave this slider enabled to schedule a backup before the migration. Otherwise, move the slider to the left to disable the option. 
  • Schedule a backup after successful migration - leave this slider enabled to schedule backups in case of successful migration. If you do not need these backups, disable the slider.
  • Delete old backups after successful migration - leave the slider enabled to remove old backups incompatible with KVM after the migration is completed. If you need these backups, disable the slider.

    If enabled, this option deletes all the old backups besides the one that is taken right before the migration provided that you also enabled scheduling a backup before the migration.

Click Next to view the migration summary of your configuration. 


At the final step of the wizard, you can see the migration summary. Click Submit to start the migration.

Note that manually added/edited disks in fstab will require to be reconfigured after migration.