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Comments on: Why My Two vCPU VM is Slow



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By: Bish

Sat, 25 Aug 2012 23:51:01 +0000

Good News! The newer ESX versions don't need to jump on the physical CPUs in one go, so it's a lot easier than valet-parking a schoolbus at times. You still want to have vCPUs =< pCPUs, of course, but with some snooping it can drop only one ready vCPU onto the pCPU pool without waiting. Yay for progress!!



By: bisu2000

Fri, 29 Oct 2010 19:11:03 +0000

We had Xeon(R) X7350 @2.93 GHZ , 2.GB of RAM on our earlier VM, We upgraded our VMs to Dual Zenon(R) X7350 @2.93 GHZ and 4.00GB of RAM but the test we are running on this new VM is almost half slower than the older one i.e with single CPU. Any help is appreciated ! Thank you ~bisu2000



By: Bob Plankers

Wed, 23 Apr 2008 20:44:51 +0000

Yeah, I think I've blogged about it before, but I ran into a customer who was having this problem and thought it'd be helpful to repeat. :-)



By: Scott Lowe

Wed, 23 Apr 2008 17:48:11 +0000

I remember VMware preaching this back in the ESX 2.x days--as you probably do--so in some ways it's still surprising that more people aren't aware of the performance implications of vSMP VMs. It's a real challenge to get customers to understand that VMs shouldn't be provisioned in the same way they used to provision physical servers. Bob, thanks for bringing this issue to light (again).



By: aharden

Wed, 23 Apr 2008 03:31:05 +0000

Like I assume you did, I found out about this the hard way. I first saw it when I tried to do 2-CPU VMs on two single-core hyperthreaded Xeons. (Back before I knew ESX better.) Nothing doing. Even on a four-core host it's questionable. On 8-core hosts I haven't found it to be a big issue (as long as 2-CPU VMs are the exception) but I completely agree that if you avoid mixing 1- and 2-CPU VMs on the same host there is less potential of a problem. Good points in your article.