Zen or VM that is the question ??, in the Virtualization + Server-Based Computing forum on BrianMadden.com

Hi All,
Just been to Citrix HQ and also visited 24hrs later a Big Partner of Citrix and have been told conflicting stories. Let me ask you the experts what you all think....

Q:\ Can XENAPP run on VMWare , or can it only run on XenServer.

One told me never to run XenApp on VMWare as it performs sluggish and it has proven issues and the other rold me it works perfectly fine in VMWare and with no issues.

I have a VMWare ESX Enterprise x 2 monster servers actually with fiber backbone, 5TB Storage, loads of RAm etc etc, and would like to leverage off it....but now I have conflicting stories...who do I beleive.

Your opinions would be great, as I really trust this forum !!

Me thinks someone is puffing smoke in your direction about XenServer/XenApp only and is trying to run up the bill for Citrix.

I run Citrix MPS 4.5 servers on VMWare 3.5 Hosts with absolutely ZERO issues. XenApp is just the newest MPS version renamed.

What I will tell you is that the success of any hypervisor rollout, regardless of manufacturer, depends greatly on the hardware that lies beneath. Bottlenecks are still bottlenecks and in a shared-hypervisor environment the bottlenecks will just be amplified by the guest systems. Reduce & eliminate the bottlenecks and your hypervisor guests will be very happy.

Otherwise the choice over which one to use comes down to a business decision, not a technological decision.

Citrix sales/sales engineers recently stopped out to my office. They advised against me running Xen on VMWare because of the "Huge performance degradation" and stated that Xenserver is specially optimized to run XenApp. The Citrix rep also repeated that "Vmware has millions of lines of code, and we only have 500,000". I say try it out for yourself. In reality, XenApp, at its core, just an add on for Terminal Services, and I have had much luck with virtual Terminal Servers.

Regards,

Russ M

That Citrix sales rep is talking rubbish.

Much like Mark I have installed PS 4 and XenApp onto Vmware before and have had no performance issues. I am running XenDesktop 2.0 on VMware at the moment, again it is running fine.

XenApp optimized to run on Xen? More sales doubletalk. He's trying to hide Xen's relative immaturity to market when compared to VMware.

I'm just surprised that they didn't tell you to buy their WAN accellerator WanScaler at the same time and tell you that ICA is optimized for that.

Think about it. XenApp/MPS runs on a Termnial Server which runs on Windows (most of the time). XenApp/MPS never ever talks to the hardware of the server directly. That is the job of the OS. The OS doesn't care which hypervisor it sits on, if any at all. Which is why MPS/XenApp runs just fine on HyperV, Xen & VMware. It never talks direclty to the hypervisor. You will never ever see the difference between those products if your hardware underneath it all is built right for the job at hand. That is the root cause of most hypervisor performance failures. People go cheap on the hardware. (Where have we heard that before?)

Wanna have some fun? Ask the Citrix sales rep why should you pay for Xen/VMWare when you could get HyperV for free with Windows 2008? That should be good for a laugh.

Evaluate the products based on your needs, not the needs of the salesman.

Interesting factoid that I just heard at a VMWare sponsored conference (so consider the source).

ESX footprint for their hypervisor is 32Mb.

HyperV footprint for their hypervisort is 2.2Gb.


Now before everyone jumps on the "Microsoft bloat" bandwagon and starts calling the hypervisor "HyperVista" there was clarification from the speaker.

Basically, VMWare believes that the hypervisor should be totally independant of the OS and therefore trys to make as little a footprint as possible. Microsoft believes that the hypervisor needs to be an integral part of the OS (naturally, coming from them). Therefore Microsoft will put more into the hypervisor roll as they believe it will lesson the burden of the OS and provides more for the OS....ergo bigger footprint.

Two different philosphies on the same technology.

Xen wasn't even mentioned, but I would be curious to see where they fall on this scale.

So what you spoke about is the Monolithic vs. Microkernelized debate.

To answer your Xen question, both Hyper-V and Xen use a Microkernal hypervisor. ESX is a Monolithic hypervisor.

Both have their good and bad points but IMO, for performance and stability I would prefer the monolithic approach.

Simple math does it for me for today's discussion.

16Gb physical memory on a box, do I want 15.9 GB for guest OS or 13 Gb?

For many hosts, that could be at least two more guest servers (with in reason, of course).

Server density is the new buzz word here.

We'll see what develops over the next 18 months. I still think that if HyperV is "just good enough", it will be a game changer for VMware and could end up being the defacto hypervisor for most networks.

I see Xen being odd man out.

(my 1 cent as we're in a rough economy)

Truth be told.

Alot of customers are running quite large implementation of XenApp on VMware. So it is definately a possibility. However you have to keep your eyes open for how to optimize both guests and hosts to deliver the application load you have to. XenApp servers are high performance machines and need to be dealt with as such. They are not to be compared to fileservers living on swapped memory and borrowed CPU.

However there are alot of suggestions of what to look for if you google for 'how to optimize Citrix on VMware'

That said, ofcourse XenServer has an advantage they can actually integrate XenApp and XenServer at the hip and get better performance. However for my customers anyway sometimes it is more important to fit into the existing environment that to squeze the last .2% performance from the hardware. They would rather pay for another Host.

So do you have VMware, sure go with VMware, are you looking for virtualization purely for XenApp servers, then XenServer will have an advantage, and i think both XenServer and VMware ESX can cater server guests in an enterprise environment, with each their limitations.

/LamerSmurf