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Chapter 3. Compute

The OpenStack Compute service is a cloud computing fabric controller, which is the main part of an IaaS system. You can use OpenStack Compute to host and manage cloud computing systems. This section describes the OpenStack Compute configuration options.
To configure your Compute installation, you must define configuration options in these files:
  • nova.conf. Contains most of the Compute configuration options. Resides in the /etc/nova/ directory.
  • api-paste.ini. Defines Compute limits. Resides in the /etc/nova/ directory.
  • Related Image service and Identity service management configuration files.

Ephemeral Storage Discrepancy with Ceph

When using Red Hat Ceph as a back end for ephemeral storage, the Compute service does not calculate the amount of available storage correctly. Specifically, Compute simply adds up the amount of available storage without factoring in replication. This results in grossly overstated available storage, which in turn could cause unexpected storage oversubscription.

To determine the correct ephemeral storage capacity, query the Ceph service directly instead. For more information, see BZ#1236473.

3.1. Overview of nova.conf

You can use a particular configuration option file by using the option (nova.conf) parameter when you run one of the nova-* services. This parameter inserts configuration option definitions from the specified configuration file name, which might be useful for debugging or performance tuning.
For a list of configuration options, see the tables in this guide.
To learn more about the nova.conf configuration file, review the general purpose configuration options documented in Table 3.17, “Description of common configuration options”.
Do not specify quotes around Nova options.


Configuration options are grouped by section. The Compute configuration file supports the following sections:
Contains most configuration options. If the documentation for a configuration option does not specify its section, assume that it appears in this section.
Configures the baremetal hypervisor driver.
Configures cells functionality. For details, see Section 3.13, “Cells”.
Configures the nova-conductor service.
Configures the database that Compute uses.
Configures how to access the Image service.
Configures additional filesystems to access the Image Service.
Configures the key manager.
Configures authorization via Identity service.
Configures the hypervisor drivers using the Libvirt library: KVM, LXC, Qemu, UML, Xen.
Configures a Redis server.
Configures a matchmaker ring.
Configures weights for the metrics weighter.
Configures Networking specific options.
Configures the OpenStack Compute API v3.
Configures RDP proxying.
Configures serial console.
Configures virtual consoles using SPICE.
Configures certificate authority using SSL.
Configures the trusted computing pools functionality and how to connect to a remote attestation service.
Configures version locking on the RPC (message queue) communications between the various Compute services to allow live upgrading an OpenStack installation.
Configures the VMware hypervisor driver.
Configures the XenServer hypervisor driver.
Configures the ZooKeeper ServiceGroup driver.