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Virtual Server - enabling both PAE and the /3GB switch?

Source: microsoft.public.virtualserver
Sent: 01/19/2006
From: "froowstie" <(email address - cut out)>
Message:

Hey all,

I've scoured the web searching for a consistent answer on this issue and am
still a little confused.

I'm designing a large-scale Virtual Server 2005 R2 implementation. The
hardware platform will be HP DL580s with 12GB of RAM running W2k3 EE. After
reading the documentation it seems apparent the PAE switch should be enabled
to allow the o/s to address the additional memory (over and above the 4GB)?
This is stated at support.microsoft.com/?kbid=283037. Is this correct?

My next question is, do I need to enable the /3GB switch as well? My
rudimentary understanding of this switch is that enabling it would free up
1GB of kernel memory for use by applications like Virtual Server. However,
there's a series of blogs on the issue
(http://blogs.msdn.com/oldnewthing/archive/2004/08/22/218527.aspx) which
seek to explore the issue further... unfortunately they are focused around
Exchange and ultimately are pretty confusing.

To further confuse matters, I have already have Virtual Server R2 running on
a system with 12GB of RAM in a POC environment. Neither the PAE or 3GB
switches are enabled, but the system is running quite happily with 12 guest
machines. Task Manager is reporting that I have 12GB of memory.... is there
something I'm missing.....

Can anyone shed any light on the matter?

Cheers,

James.

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Related Messages

Re: Virtual Server - enabling both PAE and the /3GB switch?

Sent: 01/18/2006
From: "neo [mvp outlook]" <(email address - cut out)>
Message:

This will probably sound silly coming from me, but if the hardware can
support a 64bit operating system like Windows 2003 x64 why not go that route
for the host? I'm thinking the playing the /PAE or /3GB switch game is moot
at that point and you will probably get better results in the long run.

Just my $.02
/neo

"froowstie" <(email address - cut out)> wrote in message
news:(email address - cut out)...

Show quoted text

> Hey all,
>
> I've scoured the web searching for a consistent answer on this issue and
> am still a little confused.
>
> I'm designing a large-scale Virtual Server 2005 R2 implementation. The
> hardware platform will be HP DL580s with 12GB of RAM running W2k3 EE.
> After reading the documentation it seems apparent the PAE switch should be
> enabled to allow the o/s to address the additional memory (over and above
> the 4GB)? This is stated at support.microsoft.com/?kbid=283037. Is this
> correct?
>
> My next question is, do I need to enable the /3GB switch as well? My
> rudimentary understanding of this switch is that enabling it would free up
> 1GB of kernel memory for use by applications like Virtual Server. However,
> there's a series of blogs on the issue
> (http://blogs.msdn.com/oldnewthing/archive/2004/08/22/218527.aspx) which
> seek to explore the issue further... unfortunately they are focused around
> Exchange and ultimately are pretty confusing.
>
> To further confuse matters, I have already have Virtual Server R2 running
> on a system with 12GB of RAM in a POC environment. Neither the PAE or 3GB
> switches are enabled, but the system is running quite happily with 12
> guest machines. Task Manager is reporting that I have 12GB of memory....
> is there something I'm missing.....
>
> Can anyone shed any light on the matter?
>
> Cheers,
>
> James.
>
>
>

Re: Virtual Server - enabling both PAE and the /3GB switch?

Sent: 01/19/2006
From: "froowstie" <(email address - cut out)>
Message:

I found an answer to part 2 of my question:

From Vitrual PC Guy's Weblog
http://blogs.msdn.com/virtual_pc_guy/archive/2004/12/23/331100.aspx
Please don't use /3GB - okay?
Every now and then someone will report that they are having problems
launching more than 10 or so virtual machines under Virtual Server.
Inevitably it turns out that they have enabled the /3GB boot option
(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ddtools/hh/ddtools/BootIni_de16d3ec-c437-4628-805f-8945ea598a92.xml.asp).
This option is usually recommended for applications that need lots of
memory - it increases the amount of user-mode virtual memory available from
2GB to 3GB. However it does this by reducing the amount of kernel-mode
virtual memory from 2GB to 1GB.

And unlike most applications - we use a lot of kernel-mode virtual memory -
in fact even without the /3GB switch users are most likely to run out of
kernel-mode virtual memory before running out of user-mode virtual memory.

"froowstie" <(email address - cut out)> wrote in message
news:(email address - cut out)...

Show quoted text

Re: Virtual Server - enabling both PAE and the /3GB switch?

Sent: 01/19/2006
From: "froowstie" <(email address - cut out)>
Message:

I also got some other feedback:

1.. PAE switch - the PAE switch is enabled by default for Windows 2003
Enterprise.
2.. The /3GB switch enables more app memory but "crunches" the OS memory
to 1GB which may result in more paging. Based on some MS seminars I've been
in, there's not a "solid" approach (for non Exchange/SQL solutions). I
would recommend testing with/without the /3GB switch if you have time and/or
feel that it's worth a look.
I'd suggest though, that if you have a successful implementation without
the /3GB switch, "don't fix what's not broken" and do the same on this
implementation.

"froowstie" <(email address - cut out)> wrote in message
news:(email address - cut out)...

Show quoted text

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