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This page is designed to provide you with an explanation of the terminology you will encounter during the installation process. For ease of use, the terms are listed here in alphabetical order. Terms in Italics indicate other Key Concepts in Installation.

About Flexiant Cloud Orchestrator

Flexiant Cloud Orchestrator orchestrates the Physical Resources required to create a cloud platform. It enables you to use Physical Resources to create Virtual Resources, and to manage these centrally, ensuring that they can communicate and interact to form a stable platform on which customers can run their desired software. 

Physical and Virtual Resources

Physical Resources are the hardware devices that are used to create Virtual Resources. Physical Resources include Nodes, Storage, and the Network the resources use to communicate with each other and the internet. Virtual Resources are portions of the capacity of the Physical Resources that behave like Physical Resources, but are provisioned on demand rather than in advance of demand. Types of Virtual Resource include Virtual Machines, Disks, and Snapshots.

Physical Resources


A cluster consists of a collection of one or more Nodes, combined with a Cluster Controller. Your installation of Flexiant Cloud Orchestrator has at least one cluster.

All the Compute Nodes within the cluster share:

  • The same Storage Groups;
  • The same physical network; and
  • The same Hypervisor.

Therefore, if you want to have two different Hypervisors, or use different Storage, you will need to break your Nodes into clusters.

Multiple clusters can be managed by a single Management Plane. In a simple single cluster deployment, both the Management Plane and Cluster Controller can be located on the same Node.

Clusters can be added or removed by the master billing entity, using the admin page.

The number of clusters that you are permitted to run is determined by your licence.

Cluster Controller

The control hardware for a Cluster. This passes instructions to the Cluster from the Management Plane, although in single Cluster deployments both the cluster controller and the Management Plane can be located on the same hardware.


The part of your system that allows multiple Virtual Machines to be run using hardware from different Physical Resources. Your choice of hypervisor affects the types of Network and Storage you can use. The hypervisors you can use may also be restricted by the terms of your licence.

Currently, Flexiant Cloud Orchestrator supports the following hypervisors:

  • KVM
  • Xen 4
  • VMware
  • Hyper-V
  • Virtuozzo (formerly PCS)

Management Plane

The control hardware for your installation of Flexiant Cloud Orchestrator. This passes instructions to one or more Cluster Controllers, which then pass instructions to Clusters.


The method the virtual resources in a Cluster use to communicate with each other. This is different from the physical network that connects your Compute Nodes to each other within a Cluster. Flexiant Cloud Orchestrator supports two networking modes for virtual resources: 

  • Public Virtual Internet Protocol (PVIP) - this networking mode is supported by KVM and Xen 4 Hypervisors only.
  • Virtual Local Area Network (VLAN) - this networking mode is supported by all Hypervisors. Use of this networking mode requires a Router Node to correctly determine where the network traffic for the running Virtual Machines should be sent.


A node is a physical machine dedicated to either running Virtual Machines (a Compute Node) or routing network traffic (a Router Node). Router Nodes are only required if a VLAN Network is used.

  • In a centralised Storage model, compute nodes under KVM and Xen 4 Hypervisors do not require disks as they network boot from the Flexiant Cloud Orchestrator Management Plane. Compute nodes under VMware and Hyper-V Hypervisors boot from hard disks on each Node
  • In a localised Storage model, compute nodes under KVM and Xen 4 Hypervisors boot from hard disks on each node.
  • Router nodes do not require disks and always network boot from the Management Plane regardless of which Hypervisor is used.


The physical resource on which stores data and makes it accessible to the other physical resources and the Virtual Machines. Data stored by a Virtual Machine is retained even when the Virtual Machine shuts down or loses power. The storage resource can be either a central resource or located on Compute Nodes as localised storage. Each of these options has its own advantages and disadvantages.

  • Centralised storage gives your platform increased resiliency and reduces the disruption to customers in the event that a Compute Node loses power, but hardware can be expensive and this may create scaling bottlenecks.
  • Localised storage is less resilient, as if a Compute Node loses power, the storage device must be removed from the node and placed in a working node before customers can access their Virtual Machines again. As against this, localised storage has the advantage of being cheaper and easier to scale.

Virtual Resources


Disks are individual virtual disks provisioned from a supported Storage system.


Images are templates of Disks (KVM and Xen) or Virtual Machines (VMware and Hyper-V) that have been stored on the platform in a read-only format to allow customers to duplicate them repeatedly. Images may be base Operating System templates, or can contain software that is commonly used on your Virtual Machines, for example an email client or media player. Images are created from existing Snapshots, or uploaded via the 'Fetch Image' service. 

Images can be private to the customer who created them, shared with selected other customers or users, or shared with an entire Billing Entity. Images can also have specific permissions, allowing restrictions to be placed on how they can be used. For more information, see the Example Image Permissions page.


A Network Interface Card (NIC) is a piece of hardware that allows a computer to communicate with a network. Virtual Machines have virtual NICs (vNICs) that fulfils the same role. VNICs are referred to as NICs throughout the UI and in this documentation, as there is no practical difference between the two.


A snapshot is the saved state of a Disk (KVM and Xen) or Virtual Machine (VMware and Hyper-V) at a particular point in time. A snapshot can be used to create an Image.


A subnet is a subdivision of a Network. This allows you to create Networks within Networks, so that groups of Virtual Machines can communicate with each other as though they were on the same physical network.

Virtual Machine

A virtual computer. This uses processor and RAM resources from the Compute Node and stores data on the Storage device. A virtual machine is capable of running most software that a physical computer can. If a VLAN Network is used, network traffic for the virtual machine is routed by a Router Node.

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