Maintenance Mode for Xen/KVM Compute Resources

Compute resources provide hardware for virtual servers, ensuring highly efficient use of available hardware. Below you can find the solutions regarding compute resource maintenance.

If you need to take a compute resource out of service, fix or upgrade it, use the maintenance mode feature. The VSs will be migrated to another compute resource and you can easily maintain your hardware. Be aware that after maintenance, VSs will not be migrated back to your compute resource automatically. You should manually bring VSs back to this compute resource.

If a compute resource is overloaded, but you do not want to take it out of service, you can enable or disable the ability to install/boot virtual servers on the compute resource by means of the Enabled slider while editing compute resource. Virtual servers that are already created on this compute resource will not be migrated and will be running.

  • Maintenance mode is applicable only to Xen/KVM compute resources.
  • Ensure that the Set maintenance mode for any compute resource permission is on before managing maintenance mode. For more information, refer to the List of all OnApp Permissions section of this guide.
  • Starting with OnApp 5.4, maintenance mode is also available for CloudBoot compute resources. Also, you can disable Integrated Storage for CloudBoot compute resources with Integrated Storage.

Enable Maintenance Mode


To enable maintenance mode for a particular compute resource:

  1. Go to your Control Panel's Settings menu.
  2. Click the Compute Resources icon.
  3. Click the label of the compute resource you are interested in.
  4. Click Tools > Enable Maintenance Mode.
  5. On the screen that follows:
    • Move the first slider to the right if you want to stop all virtual servers that cannot be migrated to another compute resource. This might happen because there are not enough resources on other compute resources in this zone for all VSs, or there is only one compute resource in a zone. All VSs, which have the hot migration option enabled, are attempted to be migrated to another compute resource. Note that smart servers can be migrated using only the cold migration option.
    • Move the second slider to the right if you are sure you want to enable maintenance mode for this compute resource.
  6. Click the Confirm button. The action will be confirmed only if both options are enabled.

VSs will be sequentially migrated to other compute resources within the compute zone to which your compute resource is assigned. The compute resource will be marked as in maintenance mode and you will be able to fix or upgrade it. 

Be aware that Xen-based VSs are migrated to Xen compute resources and KVM-based VSs - to KVM compute resources respectively within one compute zone. If you want to enable maintenance mode for Xen compute resource, there must be at least one more Xen compute resource within a compute zone to which both of them are assigned, otherwise, you will not be able to activate maintenance mode for this compute resource.

Disable Maintenance Mode



To bring a compute resource back online, switch maintenance mode off:

  1. Go to your Control Panel's Settings menu.
  2. Click the Compute Resources icon.
  3. Click the label of the compute resource you are interested in.
  4. Click Tools > Disable Maintenance Mode.

If you want to return VSs to the compute resource, from which they were migrated, you should manually bring VSs back to this compute resource.

Disabling maintenance mode initiates automatic reboot of a compute resource.


Maintenance Mode and Extended CPU Configuration



If the compute zone has extended CPU configuration (CPU model/flags) and one of the compute resources from this compute zone goes to maintenance mode, there are several scenarios that can take effect when the resource goes back online:

  • If the compute resource after maintenance has the same CPU performance characteristics as other compute resources in a compute zone, the CPU model remains the same for this compute zone.
  • If the compute resource after maintenance has better CPU performance characteristics than other compute resources in a compute zone, the CPU model remains the same for this compute zone.
  • If the compute resource after maintenance has worse CPU performance characteristics than other compute resources in a compute zone, the CPU model is downgraded for this compute zone.

    Consider assigning a compute resource with worse or better CPU performance characteristics to another compute zone, where a CPU model would correspond to the actual CPU performance.