Manage flavors

In OpenStack, flavors define the compute, memory, and storage capacity of nova computing instances. To put it simply, a flavor is an available hardware configuration for a server. It defines the size of a virtual server that can be launched.

note

Flavors can also determine on which compute host a flavor can be used to launch an instance. For information about customizing flavors, refer to compute-flavors.

A flavor consists of the following parameters:

Flavor ID

Unique ID (integer or UUID) for the new flavor. If specifying ‘auto’, a UUID will be automatically generated.

Name

Name for the new flavor.

VCPUs

Number of virtual CPUs to use.

Memory MB

Amount of RAM to use (in megabytes).

Root Disk GB

Amount of disk space (in gigabytes) to use for the root (/) partition.

Ephemeral Disk GB

Amount of disk space (in gigabytes) to use for the ephemeral partition. If unspecified, the value is 0 by default. Ephemeral disks offer machine local disk storage linked to the lifecycle of a VM instance. When a VM is terminated, all data on the ephemeral disk is lost. Ephemeral disks are not included in any snapshots.

Swap

Amount of swap space (in megabytes) to use. If unspecified, the value is 0 by default.

RXTX Factor

Optional property that allows servers with a different bandwidth be created with the RXTX Factor. The default value is 1.0. That is, the new bandwidth is the same as that of the attached network. The RXTX Factor is available only for Xen or NSX based systems.

Is Public

Boolean value defines whether the flavor is available to all users. Defaults to True.

Extra Specs

Key and value pairs that define on which compute nodes a flavor can run. These pairs must match corresponding pairs on the compute nodes. It can be used to implement special resources, such as flavors that run on only compute nodes with GPU hardware.

The default flavors are:

Flavor VCPUs Disk (in GB) RAM (in MB) ———– ——- ————– ————- m1.tiny 1 1 512 m1.small 1 20 2048 m1.medium 2 40 4096 m1.large 4 80 8192 m1.xlarge 8 160 16384

You can create and manage flavors with the nova flavor-* commands provided by the python-novaclient package.

Create a flavor

  1. List flavors to show the ID and name, the amount of memory, the amount of disk space for the root partition and for the ephemeral partition, the swap, and the number of virtual CPUs for each flavor:

    $ nova flavor-list
    
  2. To create a flavor, specify a name, ID, RAM size, disk size, and the number of VCPUs for the flavor, as follows:

    $ nova flavor-create FLAVOR_NAME FLAVOR_ID RAM_IN_MB ROOT_DISK_IN_GB NUMBER_OF_VCPUS
    

    note

    Unique ID (integer or UUID) for the new flavor. If specifying ‘auto’, a UUID will be automatically generated.

    Here is an example with additional optional parameters filled in that creates a public extra tiny flavor that automatically gets an ID assigned, with 256 MB memory, no disk space, and one VCPU. The rxtx-factor indicates the slice of bandwidth that the instances with this flavor can use (through the Virtual Interface (vif) creation in the hypervisor):

    $ nova flavor-create --is-public true m1.extra_tiny auto 256 0 1 --rxtx-factor .1
    
  3. If an individual user or group of users needs a custom flavor that you do not want other tenants to have access to, you can change the flavor’s access to make it a private flavor. See Private Flavors in the OpenStack Operations Guide.

    For a list of optional parameters, run this command:

    $ nova help flavor-create
    
  4. After you create a flavor, assign it to a project by specifying the flavor name or ID and the tenant ID:

    $ nova flavor-access-add FLAVOR TENANT_ID
    
  5. In addition, you can set or unset extra_spec for the existing flavor. The extra_spec metadata keys can influence the instance directly when it is launched. If a flavor sets the extra_spec key/value quota:vif_outbound_peak=65536, the instance’s outbound peak bandwidth I/O should be LTE 512 Mbps. There are several aspects that can work for an instance including CPU limits, Disk tuning, Bandwidth I/O, Watchdog behavior, and Random-number generator. For information about supporting metadata keys, see Flavors.

    For a list of optional parameters, run this command:

    $ nova help flavor-key
    

Delete a flavor

Delete a specified flavor, as follows:

$ nova flavor-delete FLAVOR_ID