KVM vs VMware ESX: which can run more virtual machines?
In a recent article written by the register , Redhat claimed that its recently acquired KVM can run 5 vms for every 3 that ESX can run when compared on the same hardware. When compared with Citrix Xenserver, citrix performs even worse. The claim was made in London this week at a journalists’ roundtable by Benny Schnaider, the CEO of qumranet. He claimed that KVM can run 52 VMs in a physical server, in which ESX can run a maximum of 35 vms on the same server.
The reason he listed for this is basically that the hardware assisted virtualization strategy that kvm uses outperforms hypervisors that need to support older chips without any hardware virtualization extensions. This does not come as a surprise to me and the gap will only widen as the chip makers continue to add more virtualization features. This goes back again to the previous article posted here on why kvm will eventually be a dominant hypervisor in the market. Benny goes on to say that KVM is also more efficient when it comes to virtualizing windows and dealing with it’s heavy memory requirements.
The original article can be found at the following link: Redhat sprints past ESX on VM running.
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Okay. This is good if it's
Tuesday, September 16, 2008 - 03:00 blinkizOkay. This is good if it's true. Real benchmark would be good here.
How about Xen
Friday, February 27, 2009 - 17:22 Anonymous (not verified)I found it hard to believe kvm outperforms Citrix XenServer since I've seen xen running a lot more vms than kvm and much faster.
Are there any benchmarks available?
The original article didn't
Friday, February 27, 2009 - 18:41 Haydn SolomonThe original article didn't provide any benchmarks or details on the tests performed but it definitely made for interesting news. It also sounds like they may have been testing windows guests since they made mention of kvms efficient use of memory for windows guests.
FUD
Thursday, April 2, 2009 - 15:24 Anonymous (not verified)This is just FUD. VMware in ESX and even hosted products has supported Intel/AMD's most advanced virtualization assist technology since it has been available.
In fact the only reason why it was at one point truthful to claim that someone else used VT and VMware didn't is because in the first iterations, processor assisted virtualization actually performed WORSE than VMware's binary translation. So VMware still used binary translation for performance reasons.
Having the capability to support processors without virtualization assist does not mean that you can't also support processors with such assists, and in fact, ESX/Workstation does use such assists where it provides benefit. Basically Redhat/KVM is trying to pretend their lack of support for older hardware is a benefit, when it is in fact just a missing feature.
-VMware developer
Re: FUD
Thursday, April 2, 2009 - 19:15 Haydn SolomonThe article was not suggesting that Vmware is unable to take advantage of hardware virtualization but rather highlighting the fact that hypervisor development has become much simpler ( in relative terms ) as a result of new hardware virtualization technology. I don't think that you can argue with this statement. I will agree that when it comes to older hardware which do not support hardware virtualization, vmware esx is pretty much king.
When it comes to linux kvm supporting older hardware for virtualization, I really don't think the linux kernel developers care about this very much nor do they pretend to. It was a conscious decision to take advantage of hardware virtualization extensions as this is where kernel developers are most comfortable; driving hardware. Were it not for the chips supporting virtualization, I don't think kernel developers would have ventured into virtualiztion. Furthermore, the trend is more virtualization features being pushed down to hardware removing more work from the hypervisor. I don't see any indication of this trend changing.
The point is that hardware virtualization is the trend. Hypervisors will become more dependent on hardware virtualization support features thereby making hypervisors more commonplace as is already becoming apparent. Performance will be more dependent on hardware than software and this is where linux shines.
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