Exchange 2003 /3GB Quick Reference

I've seen questions on the use of the /3GB switch recently in several different places, so I thought it useful to write up a very quick guide on where it should or shouldn't be used.  There are 3 basic rules for Exchange 2003:

*  Implement the /3GB switch on mailbox or public folder servers that have 1GB RAM or more.

*  If Exchange 2003 is running on Windows 2003, implement the /USERVA=3030 switch as well.

*  Do not implement the /3GB switch on front-end or routing servers, even if they have 1GB RAM or more.

Account Deleted on January 10, 2005 at 03:45 AM in How-Tos, Useful Info
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Comments

Neil why would you not use the 3Gb switch on front end or routing servers?

Jon

Posted by: Jon at Jan 11, 2005 6:53:44 PM

Should also add /NOPAE switch now with the /3GB switch. Windows 2003 detects wheather a server is hotmemory swapable and automatically turn on PAE which of course is a major no-no with Exchange.

I got caught on that one, MS has updated only some of it's documentation to reflect this.

Posted by: Korbyn at Jan 13, 2005 11:33:42 AM

I know this is an Exchange blog but what about Windows Servers in general? Such as a DC, should you implement the /3GB on a DC with more than 1 GB or RAM? What are the effects if you do\don't?

Posted by: joe at Jan 13, 2005 9:28:45 PM

Sorry for the delay in posting a comment back.

It's not recommended to put the /3GB switch on a front-end server because you'll get better scalability and performance if you don't. The /3GB switch is good for the store.exe process, but since a lot of info on a FE server passes through the kernel mode address space, shrinking this with the /3GB switch won't do the server any favours.

And yes, it's recommended to implement the /3GB switch on GC servers. More AD data will be cached rather than retrieved from disk.

Posted by: Neil Hobson at Jan 17, 2005 3:26:46 PM