Xeon Hyperthreading on Win2k server

[Mark]

My company is currently deploying new hardware for our new hosting site. We
have all new servers. 4 of them are running Win2k standard server and are
web servers, and 3 of them are win2k advanced servers running SQL Server.

We have been working on tracking down speed issues for quite a while and
recently realized (by accident) , that the webservers run WAY faster when
hyperthreading is turned off. We are using MS Application Center Test for
load testing on the servers and realized this after running some tests after
turning hyperthreading off against our web application.

I've been trying to find a clear cut answer about whether or not you should
use hyperthreading on win2k server, but I haven't found one. Although I have
seen several references to this issue and seen posts of people saying to
shut if off. It seems win2k doesn't know the difference between logical and
physical processors, so maybe that's why it's not good for win2k. ?

Does anyone know where I could find more info on this? We're going to turn
off hyperthreading on the webservers obviously because they perform better,
but I'm wondering if we will see performance gains by also shutting of
hyperthreading on the win2k SQL Servers. ?


Any insight into this would be great.

Thanks.

 

[Bob I]

Windows 2000 does not "support" HT. It sees the HT CPU as 2 processors
and treats them as such. The standard answer is that if HT works for you
great, if it causes problems then disable it in the BIOS. HT is
supported in XP and later, so if you "must" have HT, then you need to
upgrade OP systems.

 

[Rikki]

Hi Mark,

There is a whitepapers about this from Intel and
Microsoft. I hope this whitepapers will help you.

Intel:
http://www.intel.com/ebusiness/hyperthreading/server/
Microsoft:
http://www.microsoft.com/windows2000/server/evaluation/perf
ormance/reports/hyperthread.asp

Regards,

Rikki