nova/doc/source/admin/index.rst

Compute

The OpenStack Compute service allows you to control an Infrastructure-as-a-Service (IaaS) cloud computing platform. It gives you control over instances and networks, and allows you to manage access to the cloud through users and projects.

Compute does not include virtualization software. Instead, it defines drivers that interact with underlying virtualization mechanisms that run on your host operating system, and exposes functionality over a web-based API.

Overview

To effectively administer compute, you must understand how the different installed nodes interact with each other. Compute can be installed in many different ways using multiple servers, but generally multiple compute nodes control the virtual servers and a cloud controller node contains the remaining Compute services.

The Compute cloud works using a series of daemon processes named nova-* that exist persistently on the host machine. These binaries can all run on the same machine or be spread out on multiple boxes in a large deployment. The responsibilities of services and drivers are:

Services

nova-api

Receives XML requests and sends them to the rest of the system. A WSGI app routes and authenticates requests. Supports the OpenStack Compute APIs. A nova.conf configuration file is created when Compute is installed.

Describe nova-api-metadata, nova-api-os-compute, nova-serialproxy and nova-spicehtml5proxy

nova-console, nova-dhcpbridge and nova-xvpvncproxy are all deprecated for removal so they can be ignored.

nova-compute

Manages virtual machines. Loads a Service object, and exposes the public methods on ComputeManager through a Remote Procedure Call (RPC).

nova-conductor

Provides database-access support for compute nodes (thereby reducing security risks).

nova-scheduler

Dispatches requests for new virtual machines to the correct node.

nova-novncproxy

Provides a VNC proxy for browsers, allowing VNC consoles to access virtual machines.

Note

Some services have drivers that change how the service implements its core functionality. For example, the nova-compute service supports drivers that let you choose which hypervisor type it can use.

manage-volumes flavors default-ports admin-password-injection manage-the-cloud manage-logs root-wrap-reference configuring-migrations live-migration-usage remote-console-access service-groups node-down

Advanced configuration

OpenStack clouds run on platforms that differ greatly in the capabilities that they provide. By default, the Compute service seeks to abstract the underlying hardware that it runs on, rather than exposing specifics about the underlying host platforms. This abstraction manifests itself in many ways. For example, rather than exposing the types and topologies of CPUs running on hosts, the service exposes a number of generic CPUs (virtual CPUs, or vCPUs) and allows for overcommitting of these. In a similar manner, rather than exposing the individual types of network devices available on hosts, generic software-powered network ports are provided. These features are designed to allow high resource utilization and allows the service to provide a generic cost-effective and highly scalable cloud upon which to build applications.

This abstraction is beneficial for most workloads. However, there are some workloads where determinism and per-instance performance are important, if not vital. In these cases, instances can be expected to deliver near-native performance. The Compute service provides features to improve individual instance for these kind of workloads.

pci-passthrough cpu-topologies huge-pages virtual-gpu file-backed-memory ports-with-resource-requests virtual-persistent-memory

Additional guides

aggregates arch availability-zones cells config-drive configuration/index evacuate image-caching metadata-service migration migrate-instance-with-snapshot networking quotas security-groups security services ssh-configuration support-compute secure-live-migration-with-qemu-native-tls mitigation-for-Intel-MDS-security-flaws vendordata