Add New Server to your existing SharePoint 2007 Server Farm While Users connected with zero downtime

Is happens many times that you find you need to scale your environment out, by extending the number of servers of your server farm, or just adding new services to the existing farm like running Excel services on a dedicated servers.

i) You need to make sure that all MS SharePoint Server 2007 prerequisites are installed:
- IIS
- MS .NET Framework 2.0.
- MS .NET framework 3.0.
- ASP.NET.
- Additional language (if any).

Note: If the new server is an additional Web Front-end then you need to coordinate with your network team to guarantee the correct configuration of Network load balance either by Windows NLB or hardware load balancer.

ii)Install the SharePoint Binaries and all required service packs
- Run the Installation package of SharePoint 2007.
- Run the installation package of the SharePoint 2007 Language Pack (if any).

Note: if you install any of the SharePoint service pack on any server in your server farm then you should repeat the same installation on every server in the farm.

iii) Run the SharePoint Configuration Wizard on the new server, and select Add to existing server farm, you need to use select the database server hosting your SharePoint Config database and supply sufficient Username/Password to connect to that server Farm.

iv) Deploy all Strong Named assemblies to the new Server GAC on (c:\Windows\Assembly). (If you have Custom Development).

v) Deploy User Controls (if any) to the Control templates directory under the SharePoint Installation path.

vi) Modify the Web.config of every web application (If Needed), commonly you will have to add the Connection Strings, AppSettings, Register some safe controls.

Important Note: Once you enabled the Network load balance the NLB service will start forward requests to that new server, so if the server farm is in production this will cause a lot of errors to the connected user because they will be forwarded a vacant server, so I recommend to do all configuration and test the server locally before enabling NLB and after making sure that everything is ok then add it to NLB.