Why SQL Server 2008 R2 does a full installation for just adding another instance (only database engine) on the same machine? I thought it will be quick a installation, but it's not. What is SQL Server doing, copying/registering all the files again for this new instance?

Please clarify me.

  • Which version of Sql Server was already installed in your machine?
    – vijayp
    Oct 31 '14 at 6:22
  • SQL Server 2008 R2 Express
    – Ganesh
    Oct 31 '14 at 6:33

Actually Sql server has two types of component\features.
1. Instance specific features
2. Shared Features
And Database Engine, Analysis Services, and Reporting Services are part of instance specific features which has to copy many files for installing new instance.



An instance, whether default or named, has its own set of program and data files, as well as a set of common files shared between all instances of SQL Server on the computer.

For an instance of SQL Server that includes the Database Engine, Analysis Services, and Reporting Services, each component has a full set of data and executable files, and common files shared by all components.

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There is an advantage to this that will become apparent once the system has been running for a while: you can have both instances running at different release levels.

Imagine encountering a bug that is creating problems in one of your applications. There is a hotfix available, but you are not sure whether or not it will create a problem in your other applications. Simply create a new instance, install the patch and move your database over. It's not something I would enjoy doing, but it may be necessary.

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