Sql Server 2005 - A look at Installation : Instances

About Sql Server 2005 Instances:

• More than one Sql Server 2005 can be installed on the same server, each installation is an instance,
• On the same machine you can have both Sql server 2000 and also Sql Server 2005 running side by side (like i do on my laptop),
• When you install Sql Server 2005 you are asked whether you want it to be installed as a default instance (no name for the instance) or you want to give it a name.
• During installation you can look at already existing instances as shown in the figure,

Why we need multiple instances?

• If you are planning to have a test environment and a production environment i would recommend installing Sql Server Developer edition on another pc and use it as a test environment, i do not like having test and production on the same OS box. Then why do we need multiple instance support? which is a great question, my answer is below,
• When you need to have multiple versions of sql server like 2000 & 2005 each run in their own instances,
• When you need to give admin or sa access to two different administrators to maintain their own sql servers,
• When you want to have another instance on the same OS where you can first test the service packs and ensure it works fine on the production OS and then do it to the other live instance,
• When you install other software like Vault or Sharepoint Portal Server 2007 or Visual Studio IDE 2005 they install their own instances of sql server 2005 or Sql Server 2005 Express editions.