Running Multiple SQL Servers on the Same Computer

Some organizations will want to run multiple SQL Server database servers on the same computer, which improves server utilization and simplifies management. Two different technical mechanisms support this:

• Multi-instancing enables multiple independent database servers (instances) to share a single Windows installation, called an operating system environment (OSE)
• Hardware virtualization enables multiple OSEs to run on the same physical computer; separate instances of SQL Server may be running on several of these OSEs.

Multi-instancing within an OSE raises no SQL Server licensing complexity, but virtualization can sometimes require SQL Server to be licensed separately for each OSE. Organizations that make heavy use of virtualization should strongly consider SQL Server Enterprise Edition, because it offers the most favorable licensing terms in virtual environments.

Multi-Instancing

Multi-instancing enables multiple SQL Server database servers to run in the same OSE. Each instance is a unique installation of SQL Server that is installed, started, stopped, configured, and patched independently of other instances. Multi-instancing reduces the likelihood that a problem with one database application will negatively impact another, among other advantages.