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how to use 16 GB of memory

Posted on 2011-03-01
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Last Modified: 2012-06-27
Hi all,

    We are having server with windows 2003 R2 enterprise installed with 16GB of memory
we are using /3gb switch in boot.ini. We are facing memory exception error at times in server. Doubt /3GB uses all 16 GB? Or need to reconfigure?

   
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Question by:dinagaran2000
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18 Comments
 
LVL 6

Expert Comment

by:Mistralol
ID: 35006732

Is this for 2008 R2 x32 or x64?

If its the 32bit edition move to the 64bit edition.

32bit can address 4GB of memory
64bit can do much much more.

0
 
LVL 2

Expert Comment

by:namanov
ID: 35006757
Hi, you must use /PAE switch instead /3GB
Take a look here http://support.microsoft.com/kb/283037
0
 
LVL 6

Expert Comment

by:Draxonic
ID: 35006766
Windows 2008 R2 x64 can address over 16GB of memory (up to 24GB I think) without paying for the Enterprise version.
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LVL 17

Expert Comment

by:Nik
ID: 35006775
Physical Address Extension or PAE switch that is used on x86 Operating Systems cannot allocate more than 3GB of memory although once used OS can actually see all of the available memory.
The only thing you can do is to move to 64-bit OS as already suggested.
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LVL 5

Expert Comment

by:Chris-Vielife
ID: 35006784
0
 
LVL 17

Expert Comment

by:Nik
ID: 35006828
More info on this. OS Limit is 3GB as I'm aware, but the System limit is 4GB.

The 32-bit limitation is how the system is limited by the addressing space, NOT the vendor. Any more than 4 GB RAM on a 32-bit system is just not seen by the OS, but a portion CAN be used by the BIOS.
Here's the math:
2^32=4294967296 (4.29 GB)
So a 32-bit system can only address roughly 4.29 GB of RAM AT THE MAXIMUM. This is a system limit, not an OS limit.
The PAE extension is built into all modern 32-bit OS (not needed on 64-bit for obvious reasons) and basically allows a second kernel to address the remaining RAM.

http://www.microsoft.com/whdc/system/platform/server/pae/paedrv.mspx
0
 

Author Comment

by:dinagaran2000
ID: 35006993
Sorry. i am bit confused. We are using 32 bit R2 Enterprise. Whether i need to use /3gb
 (what is the syntax). or PAE to use. Pl help
0
 
LVL 2

Expert Comment

by:namanov
ID: 35007008
Hi, here is example:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Windows Server 2003, Enterprise" /fastdetect /PAE
0
 

Author Comment

by:dinagaran2000
ID: 35007201
Hi namanov

    Will it use 16 Gb fully? What we haveused ( /3Gb is wrong? will not use 16GB?)

Pl
0
 
LVL 2

Expert Comment

by:namanov
ID: 35007298
Hi dinagaran,
Yes, with PAE switch you will use 16Gb, actually you can use up to 64Gb memory,
Just enter switch in boot.ini file like described in previous post.
0
 

Author Comment

by:dinagaran2000
ID: 35007407
Thanks. i wll implement and get back to you shortly
0
 
LVL 10

Expert Comment

by:LMiller7
ID: 35008118
The /PAE switch is necessary to use more than 4GB RAM with a 32 bit OS. The /3GB switch isn't really about RAM usage at all but the virtual address space available to applications. By default the 4 GB virtual address space is divided 2 GB system and 2 GB private per process. The /3GB switch changes this to 1 GB system and 3 GB per process. But only applications that explicitly indicate they are compatible will benefit and most are not.

With the /3GB switch set the maximum RAM that can be used is 16 GB, and in practice it may be less. This switch limits the system virtual address space to 1 GB and that can cause problems, possibly those you are having, particularly with large amounts of RAM.

You should NOT be using the /3GB switch unless it is recommended for applications you are running.
0
 

Author Comment

by:dinagaran2000
ID: 35015779
Hi LMiller7,

     I went to the site just now and it is R2 32bit Ent. with 8GB memory. Ruuning Web server in IIS
and in the boot.ini it is like below

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows Server 2003, Enterprise"
 /noexecute=optout /fastdetect /3GB /USERVA=2900.

As per my understanding out of 3GB (since /3GB) 2900MB has been allotted to process. Correct?

Previously it was  /noexecute=optout /fastdetect /3GB /USERVA=3030. We faced problem. So we changed to 2900.

Since it is 8 GB memory  can we give  /noexecute=optout /fastdetect /7GB /USERVA=6900.

OR
 /noexecute=optout /fastdetect /PAE

i am bit confued



0
 
LVL 2

Assisted Solution

by:namanov
namanov earned 1000 total points
ID: 35015807
Hi Dinagaran,
/3Gb switch is address space for some applications for which is recomended usage of that switch. like LMiller7 sad.
I recommend you to use /PAE switch, .
You can't miss
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LVL 10

Accepted Solution

by:
LMiller7 earned 1000 total points
ID: 35016618
If you have more than 4GB RAM you must use the /PAE switch, otherwise only 4GB will be usable. The /3GB switch sets the virtual address space dividing line at 1 GB system and 3 GB per process. This is totally independent of how much RAM you have or how it will be used. How RAM usage will be divided between the system and processes is dynamically controlled by the system. System RAM usage by the system can never be greater than 2 GB and will usually be less, possibly much less.

The /3GB switch constrains the system address space and is not generally recommended. It should only be used when you are using applications the either require it or will significantly benefit from it. Most will not. Maximum theoretical RAM with the switch is 16 GB but may well be less in a given situation.
0
 

Author Comment

by:dinagaran2000
ID: 35017794
Thanks Namanov and LMiller7. i Will do the same and get back to you shortly.
0
 

Assisted Solution

by:dinagaran2000
dinagaran2000 earned 0 total points
ID: 35041938
Dear Namanov and LMiller7

         Thanks for the support.The PTE has been increased to 2Lakhs after /PAE.

Thanks
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Author Closing Comment

by:dinagaran2000
ID: 35081136
Great
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