I've got a 32-bit server with 16GB memory. In SQL Server, AWE is enabled. Does SQL use AWE memory for everything possible? I've also got SSAS installed on that same box, and SSAS can't use AWE memory. So I want SQL to use AWE memory as much as possible to leave as much free for SSAS as possible.
As I understand it, when you set the max server memory setting for SQL Server, it prevents the sum of normal and AWE memory from going over that limit you've set. Is there any way to tell SQL server to use as much AWE memory as it wants, but be use as little normal memory as it can?
SQL Server uses AWEonly for data cache pages in the buffer pool. As far as I know this can't be changed (in any supported fashion).Also, I could be wrong here, but I believe the 3 GB limit is per process, meaning you could have two individual processes that don't support AWE each using 3 GB on a 16 GB system - they wouldn't be limited to a grand total of 3 GB between them. Where AWE comes in is allowing a single process to use more than 3 GB by itself. I'm sure the OS guys can correct me if my assumptions about AWE are incorrect.
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We're on the right track to answering my question. Do all pages that it caches use AWE memory exclusively? (Does it use AWE whenever possible?) Will it ever cache pages using normal memory if AWE is on and there is still AWE memory available?
I've put a 1GB limit on SQL so as to leave plenty of room for SSAS. I'm wondering if removing that limit on SQL will cause it to use more normal memory, or just more AWE memory.
I'm pretty sure it's 3GB total across all processes, not per process.
|||Well, there's the buffer cache and the procedure cache. The buffer cache, which holds actual data, will use AWE if it's enabled. The procedure cache doesn't use that, but I don't believe it'll end up nearly as large as the buffer cache under normal circumstances.As for whether or not non-AWE applications are limited to 3 GB each, or 3 GB total, I think we'll need a more authoritative answer from someone on that, since it has a significant effect on how to handle the situation. This KB article makes me think it's 3 GB each, but I'm not 100% certain: http://support.microsoft.com/default.aspx/kb/283037
To get an idea of how memory is being allocated, compare the Performance Monitor counter SQLServer:Memory Manager\Total Server Memory (KB) to the amount of memory that Task Manager reports (which doesn't include AWE allocations).
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If you set max server memory, it limits how much memory, total that the database engine can use, whether it is AWE or not. I have not heard of any way to try to force SQL Server to use AWE memory first.
If you are concerned about memory, and have 16GB of RAM, you should seriously consider running 64-bit, with the "Lock Pages in Memory" right granted to the SQL Server service account. That is assuming your processors are 64-bit capable (which they should be if they are less than about two years old). I have some good DMV queries here:
http://glennberrysqlperformance.spaces.live.com/blog/cns!45041418ECCAA960!526.entry
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