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SQLIsTheDevil
Posting Yak Master
177 Posts |
 Posted - 2011-12-15 : 15:58:36
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| Hello,The server is Windows Server 2003 SP2 (32-bit), running SQL Server 2005 SP3 (32-bit). I believe the server has 4 GB of physical RAM. The machine has crashed twice in the last week and it is a production machine. From what I understand, it has AWE enabled with a maximum memory limit of 6041 MB. I never heard of AWE, but I thought this was a little suspicious and suspecting thrashing was the reason the machine crashed.(FYI, AWE is enabled and the /3GB switch is present in the boot.ini file).I devoted some time today to SQL Server's memory architecture, and I don't think I quite grasp the concept of AWE.So, Address Windows Extension (AWE) is relative to physical memory, not virtual memory (paging). If the machine only has 4GB of physical RAM, how can it use more than that, if it's not touching the paging file?Or, is the server not applying AWE correctly? That is, say I have 8 GB RAM, but Windows 2003 32-bit user space can only access 2 GB (3GB with the switch). But with AWE enabled (and page locking in memory checked), I can use an additional 4GB of RAM for SQL Server 2005 (32-bit), on top of the 4GB for Windows (3GB Windows user space + 1GB Windows kernel space), IF AND ONLY IF I have the physical RAM to support it.I'm really confused and need some guidance with this matter. I'm trying to determine if I understand AWE, how it works, and if it's contributing to the machine crashing.Thank you for any help. |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2011-12-15 : 17:41:13
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| AWE only applies to physical RAM above 4 GB on a 32 bit OS, and is not applicable to 64-bit OSes. First off check and see if you have more than 4 GB; if not, it's moot and you should disable it in SQL Server.If you are experiencing thrashing of the paging file, it's not likely to be a SQL Server issue, but rather other components trying to use memory that SQL Server is using. Are you running IIS, Exchange, or some other large Windows service on the box?SQL Server is designed to use all the RAM on the server, which is one reason it shouldn't be hosted on a machine that has other roles like IIS and Exchange.Forgive the assumption, it happens quite often and you haven't mentioned them already. |
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SQLIsTheDevil
Posting Yak Master
177 Posts |
Posted - 2011-12-16 : 09:35:22
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| Thank you for your help and response, I appreciate it.Yes, it's a dedicated server; nothing else is running on the server except SQL Server. From what I understand, AWE has nothing to do with virtual memory. I wonder if there's an outside chance that it could indirectly cause thrashing, even though it's supposed to give back to the pool of physical memory if another application requests it.To reiterate, I'm running Windows Server 2003 Standard 32-bit, which only allows up to 4 GB of physical RAM.Based on information in the following links, it seems that your viewpoint is accurate. Since I have 4GB of RAM, you're saying AWE is moot. I have the /3GB switch enabled, that I know. So, how would I allow SQL Server to recognize all 4 GB of RAM, if AWE is exclusively for configurations over 4 GB? It would seem AWE is useless on Windows Server 2003 Standard 32-bit.Thank you.http://msdn.microsoft.com/en-us/library/ms190673.aspxhttp://support.microsoft.com/kb/811891/en-ushttp://www.sqlconsulting.com/sqlmemoryswitches.shtmlhttp://www.modhul.com/2007/11/10/optimising-system-memory-for-sql-server-part-i/ |
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jeffw8713
Aged Yak Warrior
819 Posts |
Posted - 2011-12-16 : 13:46:18
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| The most you can every give SQL Server with this configuration is 3GB. You cannot give SQL Server any more than that - not possible and not something you would want to do anyways. You want to always leave some memory available for the OS - or you could end up starving the OS and causing additional performance issues.Jeff |
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Sachin.Nand
2937 Posts |
Posted - 2011-12-21 : 01:51:04
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| Even though AWE is enabled on 32 bit that memory can still be paged out incase OS is starving for memory.Only exception would be when you have locked pages in memory.PBUH |
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Need help setting up AWE-mapped memory