Possible Total Physical Memory Discrepancy

Last Post 08 Feb 2011 04:20 PM by gunneyk. 8 Replies.
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rerichards
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07 Feb 2011 03:38 PM
We are running SQL Server 2008 Enterprise 64 bit on a Windows 2008 Enterprise 64 bit (SP1) box.

We have installed 32 GB physical RAM.

The Max Server Memory Setting is set at 26624 (or, 26 GB). From my understanding, that should leave approximately 6 GB for the OS.

When I run msinfo32.exe I find the following:
Installed Physical Memory (RAM) 32.0 GB
Total Physical Memory 4.00 GB
Available Physical Memory 873 MB

What I found interesting was that the Total Physical Memory was only 4.0 GB. I was expecting to see 6.0 GB, since I have 32.0 GB Physical RAM minus the 26.0 GB max server memory.

Is there something I do not understand about the "Total Physical Memory" as reported by msinfo.exe, or is something blocking the OS from using an extra 2.0 GB?
gunneyk
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07 Feb 2011 05:30 PM
Well first off I believe msinfo32.exe is a 32 bit exe so I dont know if it accounts for everything in 64 bit properly. Just from the fact that it only see's 4GB of physical memory is a clear sign it is 32 bit focused. I would use Perfmon to see the values. A couple things to keep in mind though. The Max Memory setting for SQL Server is for the buffer pool only and there are some parts of the memory that can are not accounted for with that setting and it is possible to see several hundred more MB's than the max setting being used by sql server. So I wouldn't trust the msinfo32 and just use the perfmon counters. Also keep in mind that some internal vide cards use system memory and that gets taken off the top upon startup.
rm
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08 Feb 2011 05:50 AM
And other non-sql processes on the server use memory too.
rerichards
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08 Feb 2011 08:29 AM
What perfmon counter (or counters) then, would one use, to verify the amount of memory the OS has been allotted, is 6.0 GB in my case?

I mean, I have 32.0 GB of Physical RAM, my Max Server Memory on SQL Server is set at 26.0 GB, and SQL Server:Memory Manager>Target Server Memory shows that SQL Server is consuming 26.0 GB, but neither of those confirm that the OS has 6.0 GB allotted, other than by common sense.

Is there a counter similar to SQL Server:Memory Manager>Target Server Memory on the OS level that displays the amount of memory the OS has been allotted?
gunneyk
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08 Feb 2011 12:22 PM
The Memory category is where you want to look to see who is using what but the Memory\Available MBytes will show how much is currently free. But as rm pointed out it is not just SQL and the OS using the memory. There are lots of other "apps" that will take small chuncks out of it.
rerichards
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08 Feb 2011 12:34 PM
I am apparently not explaining myself well. Or, are you telling me that I need to add up all of the memory in the Memory\Available MBytes counter by individual process to determine the amount of memory allotted to the OS. In other words, you are telling me there is not a single OS counter that tells me (in a single, scalar return) the amount of memory (total) allotted to the OS?
rm
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08 Feb 2011 01:11 PM
There's no such single counter unfortunately.
rerichards
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08 Feb 2011 03:18 PM
I spoke to a member of the Microsoft Platform Team and was given the following KB article:

950233 The Microsoft System Information (Msinfo32.exe) tool reports the incorrect amount of physical memory in a Windows Server 2008-based or Windows Vista Service Pack 1-based computer that has more than 4 GB of physical memory installed

http://support.microsoft.com/defaul...-US;950233

I was further told that when it comes to memory utilization, not to use msinfo32.exe, but to use RamMap.

http://technet.microsoft.com/en-us/...00229.aspx

In running RamMap I was able to verify that my 6.0 GB was being utilized and all was recognized by the OS.

Thanks for your help.
gunneyk
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08 Feb 2011 04:20 PM
Just to answer your question no there is no single counter for the OS since there are so many processes that make up the OS. But that utility looks handy.
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