Servers vs. Instances
Table of Contents
Overview
Is there a difference between a Server and an Instance?
Often times the words 'Server' and 'Instance' are used interchangeably in many cloud-related discussions. Although, the technical differences between these two terms will typically not lead to incorrect statements in most cases, they can cause some confusion. In order to prevent misinterpretations during collaborative efforts with your team or interacting with RightScale Technical Services, it's important to have an accurate, baseline understanding of each term.
Definitions
Instance
A virtual machine running in the cloud.
Server
The collection of properties and attributes that define a virtual machine that has run, will run, or is running in the cloud.
Since instances in the cloud can be launched and terminated several times throughout the lifetime of your web application, it's important that you can easily manage these different iterations of what are essentially different incarnations of the "same" Server that typically serve the same purpose over time. (e.g. PHP Application Server)
ServerTemplates are the "templates" that are used to create Servers. The only way to create a Server in the RightScale platform is to start with a ServerTemplate, which serves as the base configuration template for a Server. A Server will inherit a majority of its configuration from its ServerTemplate, however configurations can be overwritten at the Deployment or Server levels. (See Inheritance of Inputs.) When you create a Server, it must be placed inside a particular Deployment. A Deployment is a collection of related Servers that help satisfy the requirements for a common project. A Server cannot exist outside of the context of a Deployment. When you create a Server using a ServerTemplate, you must specify into which Deployment the Server will be placed.
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