Using flavors to create a new cloud server

When you create a cloud server, you establish its basic configuration by selecting from the available flavors. Similar flavors are grouped as flavor classes.

A flavor is the definition of the characteristics and resources that are assigned to a cloud server when it is created.

For example, you can create a 1 GB server by selecting the General Purpose flavor class and the 1 GB General Purpose v1 flavor. By making one choice of a flavor, you create a server with the following characteristics:

  • Flavor ID:

Flavor ID

The flavor’s unique identifier, ID, is used in the API to specify a desired flavor.

For example, general1-1.

Flavor IDs are returned by the List Flavors API operation, described in the Cloud Servers API documentation.

Flavor description

description is the friendly name for the flavor.

For example, 1 GB General Purpose v1.

Flavor memory

memory is the amount of RAM, available to this flavor, specified in megabytes.

For example, 1 GB of available RAM.

Flavor disk / system disk

Sometimes also called boot disk, flavor disk / system disk describes the size of the first disk that the server will attempt to access and boot from, much like the first physical hard drive plugged into a physical computer.

For example, a general1-1 server has a 20 GB system disk.

Ephemeral / data disk

Data disk space, versus system disk space, is additional disk space spread across one or more virtual disks, available to use for application data, caching, or other scenarios.

Not all flavors have data disks assigned to them. For example, the general1-1 flavor provides no data disk.

In addition, there are some important things to be aware of when using data disks:

  • Data disks are not captured when a snapshot/image of your server is created; only the system disk is captured. Using a backup solution such as Rackspace Cloud Backup is highly recommended if you use data disks to store critical data.

  • Data disks may need to be formatted, partitioned, or grouped into a software RAID group. The data disks are provided as empty or raw disks in some cases to allow you maximum flexibility in using them.


Swap is the size of an additional partition provided to your instance that would generally be used by Linux for swap memory space.

Rackspace does not provide a swap partition for most flavors, as it can degrade performance or hide memory usage issues.

Rackspace recommends choosing a server flavor with enough RAM to support your application without the use of swap.


vCPUs is the number of virtual CPU cores available to this flavor. This is important when planning and deploying applications that are multi-threaded or CPU constrained.

For example, the general1-1 flavor has 1 vCPU assigned.

Depending on the flavor, vCPUs may be provided exclusively to your instance, or may be shared in a time-slicing fashion with other virtual machines.

RXTX factor

The amount of aggregate outbound bandwidth across all attached networks (PublicNet, ServiceNet, Cloud Networks) on your Cloud Server.

For more information on the different networks available to your Cloud Server, see Working with networked Cloud Servers.

Maximum outbound public bandwidth is limited to 40% of the aggregate, while inbound traffic is not limited. In the case of the general1-1 flavor, aggregate bandwidth of 200 Mb/s (Megabits per second) means that you can generate 80 Mb/s of outbound traffic.