Flavors are a combination of the number of virtual CPUs, RAM and disk size that can be allocated to an instance.

Flavors that are accessible to all users are public flavors. Some flavors that are accessible only to a selected few users, and are invisible to all the other users, are called private flavors.

Flavors comprise predefined flavors, and user-defined or custom flavors.

Predefined Flavor

The predefined flavors are public flavors, by default. Platform 9 provides five predefined flavors. The following table describes the predefined flavors.

Flavor name Number of Virtual CPUs (vCPU) Random Access Memory (RAM) Disk Space
Tiny 1 512 MB 1 GB
Small 1 2 GB 20 GB
Medium 2 4 GB 40 GB
Large 4 8 GB 80 GB
XLarge 8 16 GB 160 GB

Custom Flavor

A custom flavor can be configured according to the user’s requirement if the predefined flavors are unsuitable for use.

Zero Disk Size Flavor

When a virtual machine is deployed using an image by applying a flavor to it, OpenStack tries to deploy the virtual machine with the disk size that is specified by the flavor.

If the disk size specified by the flavor does not match the minimum disk size required by the image, the virtual machine deployment fails.

To simplify this, OpenStack supports creation of zero disk-size flavors.

When a virtual machine is created by using a zero disk-size flavor, OpenStack configures disk size of the virtual machine to be the virtual disk size specified in the image from which the instance is being created.