Hosts and Clusters on

Overview

Mon, 17 Feb 2025 00:00:00 +0000

A Host is a server (physical or virtual) that provides compute capacity for cloud workloads, such as Virtual Machines or Kubernetes Clusters. Hosts must be connected to and controlled by one or more OpenNebula Front-end servers. To learn how to prepare Hosts, read the Cluster section of the installation guides. A Cluster is a logical grouping of OpenNebula resources including Hosts, Virtual Networks and datastores. Hosts are usually logically grouped within Clusters, but may exist independently of a Cluster object.

Host Management

Mon, 17 Feb 2025 00:00:00 +0000

In order to use a physical or virtual server as a Host, you must first prepare the server with a hypervisor and configure it to be added to OpenNebula as a Host, refer to the guides to prepare a KVM node or an LXC node.

Once you have prepared your physical or virtual nodes, you can add them to OpenNebula as Hosts. To add a Host only its hostname and type is needed.

Cluster Management

Mon, 17 Feb 2025 00:00:00 +0000

Clusters group together Hosts, datastores, and virtual networks that are configured to work together. A Cluster is used to:

Ensure that VMs use resources that are compatible.

Assign resources to user groups by creating Virtual Private Clouds.

Clusters should contain homogeneous resources. Note that some operations like live migrations are restricted to Hosts in the same Cluster.

The requirements for live migrating VMs between Hosts of the same Cluster are that no differences occur in the following areas of the hypervisors:

Virtual Topology and CPU Pinning

Mon, 17 Feb 2025 00:00:00 +0000

Overview

In this guide you’ll learn to set up OpenNebula to control how VM resources are mapped onto the hypervisor ones. These settings will help you to fine tune the performance of VMs. We will use the following concepts:

Cores, Threads, and Sockets: A computer processor is connected to the motherboard through a socket. A processor can pack one or more cores, each one implements a separate processing unit that shares some cache levels, memory, and I/O ports. CPU cores’ performance can be improved by the use of hardware multi-threading (SMT) that permits multiple execution flows to run simultaneously on a single core.
NUMA: Multi-processor servers are usually arranged in nodes or cells. Each NUMA node holds a fraction of the overall system memory. In this configuration, a processor accesses memory and I/O ports local to its node faster than those of non-local ones.
Hugepages: Systems with big physical memory also use a large number of virtual memory pages. This big number makes the use of virtual-to-physical translation caches inefficient. Hugepages reduces the number of virtual pages in the system and optimizes the virtual memory subsystem.

In OpenNebula the virtual topology of a VM is defined by the number of sockets, cores, and threads. We assume that a NUMA node or cell is equivalent to a socket and they will be used interchangeably in this guide.