Chapter 1. Concepts

To use the first generation Cloud Servers API effectively, you should understand several key concepts:

 1.1. Server

A server is a virtual machine instance in the Cloud Servers system. Flavor and image are requisite elements when creating a server.

 1.2. Flavor

A flavor is an available hardware configuration for a server. Each flavor has a unique combination of disk space, memory capacity and priority for CPU time.

 1.3. Image

An image is a collection of files used to create or rebuild a server. Rackspace provides a number of pre-built OS images by default. You may also create custom images from cloud servers you have launched. These custom images are useful for backup purposes or for producing “gold” server images if you plan to deploy a particular server configuration frequently.

 1.4. Backup Schedule

A backup schedule can be defined to create server images at regular intervals (daily and weekly). Backup schedules are configurable per server.

 1.5. Reboot

The reboot function allows for either a soft or hard reboot of a server. With a soft reboot, the operating system is signaled to restart, which allows for a graceful shutdown of all processes. A hard reboot is the equivalent of power cycling the server.

 1.6. Rebuild

The rebuild function removes all data on the server and replaces it with the specified image. Server ID and IP addresses remain the same.

 1.7. Resize

The resize function converts an existing server to a different flavor, in essence, scaling the server up or down. The original server is saved for a period of time to allow rollback if there is a problem. All resizes should be tested and explicitly confirmed, at which time the original server is removed. All resizes are automatically confirmed after 24 hours if they are not confirmed or reverted.

 1.8. Shared IP Address

Public IP addresses can be shared across multiple servers for use in various high availability scenarios. When an IP address is shared to another server, the cloud network restrictions are modified to allow each server to listen to and respond on that IP address (you may optionally specify that the target server network configuration be modified). Shared IP addresses can be used with many standard heartbeat facilities (such as, keepalived) that monitor for failure and manage IP failover.

 1.9. Shared IP Group

A shared IP group is a collection of servers that can share IPs with other members of the group. Any server in a group can share one or more public IPs with any other server in the group. With the exception of the first server in a shared IP group, servers must be launched into shared IP groups. A server may be a member of only one shared IP group.

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