I believe, from a past conversation, that disabling hyper-threading on bridgehead servers with lots of inbound connections, i.e. in enterprise deployments, should be *considered* as the replication queue has two parallel threads for processor, core or hyper threading processor as the system call sees all in the same way -multiple processors.  However, there's no real guideline here as there are so many variables, i.e. amount of change, compression, new objects, mods, whether the data is in cache or not, etc.
 
I don't think it matters all that much for the AD stuff.  You might need to look into the FRS side of things (in big environments).  It will matter for CPU-intensive apps that weren't written directly for multiple-processor systems.  Under such circumstances, it is often recommended to disable hyper threading. 
 
For example, you have to disable HT for SAP servers.  I don't think SQL cares as that is written for multiple-CPU support and can probably tell the difference between two physical processors and HT processors but don't know.  Like Al said, check the Virtual Server readme, as NIC teaming isn't supported for the host, apparently (unless, like AD, that's just load-balanced teaming).
 
 
--Paul
----- Original Message -----
Sent: Tuesday, August 08, 2006 2:11 PM
Subject: Re: [ActiveDir] DCs & Hyper-Threading


From Tim Mangan's whitepaper on hyperthreading under 2003:
"The results in this paper are exclusively related to Windows Server 2003. We are currently running the tests used in the development of this paper under  erver
2000. We can verify reports of performance and stability problems with Hyper-Threading on Windows 2000 Server, and at this time recommend customers disable Hyper-Threading under 2000."
http://www.tmurgent.com/images/WP_HyperThread.pdf

So disable under 2000 is the recomendation, As to 2003 he shows a small performance increase in all cases except multithreaded CPU-bound applications, which is expected. Personally I leave hyperthreading turned on for my 2003 installs. It also makes single->dual cpu upgrades easier since the SMP kernal is already used =)

Thanks,
Andrew Fidel



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08/07/2006 09:45 AM

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[ActiveDir] DCs & Hyper-Threading





What are people's views on whether to enable or disable hyper-threading on a Proliant box running Windows 2003 as a DC.  I remember Intel advised HT to be disabled on Windows 2000 but has this changed for Windows 2003?.  Are the performance benefits significant for a DC?
 
 
Thanks
David
 
 
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