Hi, Hyperthreading (HT) creates a real moral problem for me, even on Windows server 2003. It has obvious performance advantages that you can easily see on an HT aware operating system. BUT, when you get to a scenario where a system is doing a serious amount of work, things can fall apart a lot faster on an HT system than on a non-HT system. So HT gives me a significant advantage at low to medium levels of CPU utilization, but when things max out I'd rather not be running HT because it starts falling apart. It's a bit like the redline on a tacho, stay below the redline and life's sweet, go above and things could blow. So you have to be a bit pragmatic. Scale your TS systems so they won't hit the wall and you get all the advantages of HT with no problems. When things start getting too busy, add more servers. Some sort of CPU limitting software (TMULimit, Appsense performance suite, Tscale/Expedian, Armtech, Threadmaster) to control runaway threads is absolutely mandatory if you want a quiet life with HT. On file/print servers (2003) I've had some really painful personal experience about what can happen with HT when a server (2003 cluster) gets too busy. I'd really rather take a 10-20% dip in performance than have a file server cut out on me unexpectedly, hanging all the TS systems. But if you scale things properly and be careful about tuning antivirus settings etc, and add extra capacity when it's needed, you can benefit from HT at minimal risk. Regards, Rick Ulrich Mack Volante Systems Ltd 18 Heussler Terrace, Milton 4064 Queensland Australia. Ph: +61 7 3246 7704 email: rmack@xxxxxxxxxxxxxx web: www.volante.com.au -----Original Message----- From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Mangan Sent: Friday, 1 October 2004 8:04 AM To: thin@xxxxxxxxxxxxx Subject: [THIN] Re: Hyperthreading I did a lot of testing with it last year. I never saw it cause an error, but things often stall due to the idle processing clearing out too much on the chip when one of the logical processor idles. It caused erratic performance. Under a heavy load it *might* cause a crash, but I never saw one. I would definitely disable HT under 2000. -----Original Message----- From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Sent: Thursday, September 30, 2004 9:50 AM To: thin@xxxxxxxxxxxxx Subject: [THIN] Hyperthreading Has anybody experimented with Hyperthreading On -vs- Off on Win2k servers? I've heard rumblings that it can be problematic, and perhaps decrease performance. I noticed that most SpecInt. winners have it disabled. I'm considering disabling it on one of my farm servers to observe the results. If anybody else has experimented I'd love to hear about it. Thanks in advance, Bob ******************************************************** This Weeks Sponsor RTO Software Do you know which applications are abusing your CPU and memory? Would you like to learn? -- Free for a limited time! 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