/3GB switch doesn’t work for SharePoint anymore!
As per the best practice guidelines I have been recommending the use of the /3GB switch for WSS v2 and SPS 2003 installations, as I am sure may of you have been. I have also been using these best practice setting for MOSS 2007 and WSS v3 installations, that has all been turned on its head with this post from Microsoft.
The Windows Server 2003 /3GB switch is not supported in Windows SharePoint Services 2.0 or in later versions or in SharePoint Portal Server 2003 SP2 or in later versions – this includes MOSS 2007 and WSS v3!
The ability to use the /3GB switch in Windows SharePoint Services was eliminated when large file support was introduced in Windows SharePoint Services 2.0 Service Pack 2 (SP2). Large file support requires using large kernel mode memory buffers that cause instability in Microsoft Internet Information Services (IIS) 6.0 when the /3GB switch is used.
Reducing the size of the kernel mode memory buffers when in /3GB mode causes unacceptable performance in Windows SharePoint Services file-transfer operations. Therefore, a decision was made not to support the /3GB switch in Windows SharePoint Services. Windows SharePoint Services will run if you use the /3GB switch. However, the operating system will become unstable in scenarios in which the server is under stress.
Microsofts solution to this is to use 64bit installation, although this is not an option at the current time due to various issues like this example on SUGUK site.
It will also mean that a lot of current installation will need to be revisited as they have been designed and tested using the 3GB memory available to the application pools.
