November 1, 2005 at 6:04 am
I have 12 gigs of memory on each server in a cluster. Each server carries about the same load. In this case I should allot 5.5 gigs to each server and leave 1 gig for the OS? Is 1 gig enough for the OS?
I should use the /3GB switch and set the max server memory to 5.5 for
each server. Is that correct?
thanks
November 1, 2005 at 7:28 am
In windows boot.ini, add /3GB /PAE
Enable AWE in SQL server set the max server mem to 5.5GB.
November 2, 2005 at 9:13 am
Wouldn't you want to allocate about 10 GB to SQL on each server?
So long, and thanks for all the fish,
Russell Shilling, MCDBA, MCSA 2K3, MCSE 2K3
November 2, 2005 at 9:19 am
Once you jump to PAE, there is a need to get lots of RAM for the OS to switch in and out of. I thought that at 8GB, you needed 1GB just for the page swapping. I think I might go to 1.5 or 2GB to be safe and run SQL at 4.5GB.
This assumes that you are running an active/active cluster and want no performance loss in there's a failure. I might assume there wouldn't be a failure and run with some performance loss if there is and allocated more like 7GB to each instance, leaving 3GB for the failed instance.
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November 2, 2005 at 12:45 pm
According to MS documentation (which I can't find...) for every four gigs of RAM installed, one gig needs to be reserved for the o/s.
4GB = 1GB Reserved
8GB = 2GB Reserved
12GB = 3GB Reserved...
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November 3, 2005 at 12:17 pm
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/adminsql/ad_1_server_1fnd.asp
Before you configure Windows 2000 for AWE memory, consider the following:
However, if there is more than 16 GB of physical memory available on a computer, Windows 2000 needs 2 GB of virtual memory address space for system purposes and therefore can support only a 2-GB virtual address space.
In order to allow AWE to use the memory range above 16 GB, be sure the /3gb parameter is not in the boot.ini file. If it is, Windows 2000 will be unable to address any memory above 16 GB. When allocating SQL Server AWE memory on a 32-GB system, Windows 2000 may require at least 1 GB of available memory to manage AWE. Therefore, when starting an instance of SQL Server with AWE enabled, it is recommend you do not use the default max server memory setting, but instead limit it to 31 GB or less.
November 17, 2005 at 5:35 pm
Just my .02 ....
If you do have an active/active cluster, then it might be a good idea (as Steve suggested) to set your max memory configuration to 5 GB for each server. That way, if one server has to bear the load of both instances, you end up leaving the OS in good enough shape that it won't have to struggle to manage the memory.
However, it does seem like a huge waste to not try to take advantage of all of that extra RAM on each machine ... so you can maybe set them both up to use as much RAM (leaving at least 2 GB for the OS to do what it needs to do), with the knowledge that in a failover situation, memory management will be a problem that someone will have to manually intervene and fix.
On a related note, I have recently discovered that (contrary to popular belief) you do not have to add the /3GB boot.ini switch as it is suggested by various sources throughout the Internet. This blog may help explain why ...
http://blogs.msdn.com/oldnewthing/archive/2004/08/05/208908.aspx
Also, from the same blogger .. this myth about PAE is also interesting ...
http://blogs.msdn.com/oldnewthing/archive/2004/08/18/216492.aspx
And if you like reading, here is some more info that has links to some OS-level information regarding PAE.
http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx
Good luck!
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