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JamesNT
Moderator
USA
3151 Posts
Status: offline |
 Posted - 11/01/2011 : 11:17:49 AM
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I have a server with two E5504 quad core procs. These procs are NOT hyper-threaded. The problem is that with two virtual machines and the host I am out of virtual processors.
2 for the host
4 for the 2003 terminal server
2 for the sql server
= 8 vProcs which accounts for all 8 cores (4 cores per proc).
In order to get more out of this machine, I thought about upgrading to E5520's (these are also quad cores) which are hyper-threaded. This way, I would have more virtual procs and, therefore, can put more virtual machines on this server.
Question: Will this affect performance of the Terminal Server or are 4 vProcs from a non-hyperthreaded proc the same as 4vProcs from a hyperthreaded proc?
JamesNT
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James Summerlin
www.jamessummerlin.com |
Edited by - JamesNT on 11/01/2011 11:20:59 AM |
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Playwell
Honorable But Hopeless Addict
Netherlands
4828 Posts
Status: offline |
Posted - 11/01/2011 : 11:44:19 AM
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It's always advisable to turn on hyperthreading.
A core with hyperthreading is like a small highway. 2 small cpu payloads can run parallel and pass each other, but for big payloads you have to wait until the payload takes an exit.
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'People who think they know everything are a great annoyance to those of us who do. '
Quote by Isaac Asimov
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
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Playwell
Honorable But Hopeless Addict
Netherlands
4828 Posts
Status: offline |
Posted - 11/01/2011 : 12:12:44 PM
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| The article does not contradict me luckily :) |
'People who think they know everything are a great annoyance to those of us who do. '
Quote by Isaac Asimov
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jaxdave
Honorable But Hopeless Addict
USA
2429 Posts
Status: offline |
Posted - 11/01/2011 : 12:13:45 PM
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| Not long ago it wasn't the best practice but with today's new processors always turn it on as Ton suggested. |
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wkasdo
Administrator
Netherlands
7424 Posts
Status: offline |
Posted - 11/01/2011 : 12:35:45 PM
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> I have a server with two E5504 quad core procs. These procs are NOT hyper-threaded. The problem is that with two virtual machines and the host I am out of virtual processors.
Is there a problem with CPU overcommitment, i.e. using more vProcs than you have cores? http://blogs.technet.com/b/virtualization/archive/2011/04/25/hyper-v-vm-density-vp-lp-ratio-cores-and-threads.aspx
It's a good way to better utilize the full CPU power of the host. The flip side of this configuration is that you can max out the physical CPU, limiting performance.
> 4 for the 2003 terminal server
That's unsupported. Windows 2003 should have 1 or 2 vCPU's. There, I just gave you 2 vCPU's back ;-)
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Make it as simple as you can, but not simpler -- Albert Einstein |
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wkasdo
Administrator
Netherlands
7424 Posts
Status: offline |
Posted - 11/01/2011 : 12:39:07 PM
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| Let me qualify that last statement. Not only is 4 vCPU on 2003 unsupported, performance with 2 vCPU's might actually be better than a 4-vCPU 2003 VM. |
Make it as simple as you can, but not simpler -- Albert Einstein |
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
Posted - 11/01/2011 : 12:42:47 PM
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wkasdo,
I may need to give overcommit a second look. I only need to add an Exchange Server to this machine and the Exchange along with SQL will sit on their butts most of the time.
Not in this case. Once I added the second pair of CPU's, people started reporting that their performanc lag went away.
Where is it documented that 2003 with 4 vCPU's is unsupported? The guys at Virtual Reality Check actually recommended 4 vCPU's at one point.
JamesNT |
James Summerlin
www.jamessummerlin.com |
Edited by - JamesNT on 11/01/2011 12:46:25 PM |
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
Posted - 11/01/2011 : 12:48:10 PM
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So, with CPU overcommit I can add another virtual machine with 2 vCPU's to have this:
2 for the host
4 for the 2003 terminal server
2 for the sql server
2 for the Exchange 2010 server
= 10 vProcs which accounts for all 8 cores (4 cores per proc) with an overcommit of 2
This is acceptable assuming the terminal server is the only one with heavy load?
JamesNT
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James Summerlin
www.jamessummerlin.com |
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wkasdo
Administrator
Netherlands
7424 Posts
Status: offline |
Posted - 11/01/2011 : 1:16:24 PM
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> Where is it documented that 2003 with 4 vCPU's is unsupported?
It says so here: http://technet.microsoft.com/en-us/library/cc794868(WS.10).aspx
Actually, Mark's book on 2008R2 says the same thing.
> The guys at Virtual Reality Check actually recommended 4 vCPU's at one point.
Fine for 2008 and up, not for 2003.
> This is acceptable assuming the terminal server is the only one with heavy load?
Should not a problem. If you reduce the vCPU for the TS to two, you don't even have CPU overcommit. |
Make it as simple as you can, but not simpler -- Albert Einstein |
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
Posted - 11/01/2011 : 1:28:17 PM
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wkasdo,
It appears I need a second terminal server, then. Reducing the vCPU's to two for the one I have now will reintroduce lag.
JamesNT |
James Summerlin
www.jamessummerlin.com |
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Rambler
Major Contributor
Czech Republic
956 Posts
Status: offline |
Posted - 11/01/2011 : 1:38:07 PM
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quote:
Not only is 4 vCPU on 2003 unsupported, performance with 2 vCPU's might actually be better than a 4-vCPU 2003 VM.
Possibly on H-V, but we were running 4 vCPUs 2k3 terminal servers on ESXi and they definitely performed better than when having only 2 vCPUs :) Wasn't the argument only about scaling from 1vCPU to 2 (or 4) - because of the HAL change? |
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
Posted - 11/01/2011 : 1:42:39 PM
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It appears the "gut test" is going to win out on this one.
JamesNT |
James Summerlin
www.jamessummerlin.com |
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wkasdo
Administrator
Netherlands
7424 Posts
Status: offline |
Posted - 11/01/2011 : 2:28:53 PM
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> Wasn't the argument only about scaling from 1vCPU to 2 (or 4) - because of the HAL change?
Nope. I saw testdata for Windows 2003 that showed that scaling was definitely non-lineair going from 2 to 4 vCPU. In most cases 4 vCPU was indeed faster (not all), but two VM's with each 2 vCPU beat the VM with 4 vCPU.
From that sort of result, it was decided to take the 4 vCPU variant out of the test matrix. So yes, it wil probably work just fine AND be faster than 2 vCPU (but not twice as fast!), but it's unsupported. |
Make it as simple as you can, but not simpler -- Albert Einstein |
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JamesNT
Moderator
USA
3151 Posts
Status: offline |
Posted - 11/01/2011 : 2:56:15 PM
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I think I'm just about ready to settle on the idea of setting up a second 2003 TS and getting those hyper-threaded quad core procs. I can get two E5520's for just under $1000.00 from Dell brand-new.
JamesNT |
James Summerlin
www.jamessummerlin.com |
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wobble_wobble
Honorable But Hopeless Addict
Ireland
4523 Posts
Status: offline |
Posted - 11/01/2011 : 3:51:31 PM
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James,
maybe I'm missing something, but what % of CPU usage are you at?
Why do you think over-commiting CPU will result in latency for the users.
If you talking about having 90 TS users on a virtual guest, isn't that supposed to be the require an extra 30% resources, or did that change?
Also, as I understand it, HyperV does not allow us to specify a Core for the processing on a guest, so technically, your guests could all be running on a single core, and therefore your Host, SQL and TS could all be using the same core...or did that change?
The reason I suspect your seeing a boost on performance is because of the sharing of the cores. But unless your at 80% CPU, I'd add guests or suggest moving to a different Hypervisor as opposed to spending 1000 dollars.
My 2cent.
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Joe
After everything that has happened during the month of Jan 07, I do believe that pigs fly backwards!
http://whatismyv6.com/ |
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Hyper-Threaded vs Non-Hyper-Threaded
