Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

jasperk — Thu, 08 Dec 2005 00:27:09 GMT

excellent summary! You can spend a few days reading INSIDE WINDOWS 2000 or you can read this!

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Dmitri G — Thu, 08 Dec 2005 01:42:02 GMT

Windows 2003 Server Standart doesn't support "the /3GB startup switch in the server's boot.ini file.
See "http://blogs.msdn.com/oldnewthing/archive/2005/
11/18/494442.aspx"

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Vytas — Thu, 08 Dec 2005 18:00:54 GMT

I think people throw the entire "/3GB" switch around entirely too carelessly. Do a search on it and you will see that most articles fail to mention the limitations on which OS/versions you can actually run it on.

Kudos for mentioning the limitations in the article, although it would be nice to get a clarification on the Server 2003 Standard issue.

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Exchange — Thu, 08 Dec 2005 20:44:21 GMT

Dimitri and Vytas,

Thanks for bringing this up, as it should be mentioned.

The "support" of /3gb on W2003 Standard has gone back and forth (which does not make it easy, I know) - but in the end, it is supported in the following way:

"We support the use of the /3GB switch in Microsoft Windows Server 2003 Standard Edition in a production environment for use by Active Directory. Microsoft Exchange Server 2003 is supported in a production environment when you use this functionality. Otherwise, the /3GB switch in Windows Server 2003 Standard Edition is only for development and testing purposes."

This is from:

328882 Exchange memory use and the /3GB switch
http://support.microsoft.com/default.aspx?scid=kb;EN-US;328882

Dimitri, even the article that the blog post you point to links to has been updated since the blog post was made so W2003 Standard is listed as a supported platform for it.

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Rob D. — Fri, 09 Dec 2005 03:29:36 GMT

Excellent article. Thanks for explaining that Windows 2003 Standard supports the /3G switch with AD and Exchange. I just read that KB article a day or two ago, but missed that part.

My question is, when should you use the /3G switch? If you have a server with 4 GB of physical memory, should you use it? What if the server has 6 or 8 gigs? Is there an easy perfmon or ExBPA test to indicate that you need more kernel memory?

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Steve S — Fri, 09 Dec 2005 11:08:03 GMT

The above questions are answered in http://support.microsoft.com/default.aspx?scid=kb;en-us;823440. Short answer is that you should use the /3GB switch if >1 gig RAM is installed. Don't bother installing more than 4 gigs RAM on an exchange server.

EXBPA has a new configuration file that goes into more detail (see the post for Dec 6th).

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Mike Lee — Sat, 10 Dec 2005 01:44:16 GMT

A couple of extra details on comments about /3GB on Windows Standard editions and having more than 4 GB of RAM in a server:

(1) In Windows 2000 Standard edition, the /3GB switch did not work correctly. I don't just mean it had no effect--it could have very bad effects. It worked kind of halfway and could blue screen you.

For Windows 2003, the /3GB switch works correctly for Standard, Enterprise and Datacenter versions. The Windows and Exchange teams need to get together and agree on the supportability statements, obviously. On the Exchange side, we've had no problems due to Standard with the /3GB switch, and a lot of people are doing it.

(2) The best practice if you have more than 4GB of physical RAM in an Exchange server is to actually, physically remove it from the box. You can also disable it with registry keys for the same effect. However, if you leave it enabled, it will, just by being there, eat up some more kernel resources that are better allocated to other uses.

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Peter — Thu, 15 Dec 2005 00:48:13 GMT

I was also under the impression that applications had to be compiled with the /LARGEADDRESSAWARE switch set in order to take advantage of the /3GB setting.

See this article:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/memory/base/4gt_ram_tuning.asp

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Paul Bowden [MSFT] — Fri, 30 Dec 2005 05:35:05 GMT

That's correct Peter, and the main Exchange binaries are compiled with this switch set.

re: Microsoft Windows Kernel Memory Management and Microsoft Exchange Server

Michael Tsang — Tue, 10 Jan 2006 07:04:52 GMT

What happen if I have a Windows 2000 Advanced Server w/4GB of memory running Excahnge 2000. Do I need to fine tune anything? Specially on the pagefile settings.

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