A short guide to virtualizing Presentation and Terminal servers on VMware ESX 3

Hey Guys,

 Had a few comments from readers about their experiences with virtualized terminal services and citrix. Only a few have had any good experiences and i would like to point out more clearly that this article is in no way meant to encourage virtualizing your entire TS or Citrix Farm, it is meant as an aid to make the experience the best possible with a more or less virtualized TS or Citrix platform. Virtualizing part of the farm is also in my oppinion a strong tool in preparing for a possible disaster recovery.

/LamerSmurf

We moved to a virtual citrix farm and if we could go back to physical we would.  We were expecting great things using vmware and citrix but that is not the case.  we only use standard apps like Office and a few 3rd party citrix certified apps and as soon as we hit 18 users per Server the farm dies :-( When we have 2000+ concurrent users this is a problem as we have 80 Virtuals (25-28 Users per box).  We've started to add our old kit (Physicals) into the farm and from some extensive testing users notice performance improvement on a physical when the same amount of users are connected to a physical or virtual. 

Spend your money on physical Servers instead

I dont think anyone really suggests virtualizing everything should improve performance compared to physical hardware. However virtual hardware has benefits too and as a wise man said not too long ago "its really a question of seeing the tools we have and apply them in the situations where they most beneficial". Virtualizing, Streaming, monitoring, optimizing ... Tools.. for us to apply where we get the best use.

Using a hammer to put a screw in a wall IS possible, but it is alot more elegant and beneficial to use a screwdriver.

/LamerSmurf

Could not agree more about the LSI Logic storage adapter.  We have also found that there are different flavors of this beast, some of which exhibit complete lockups under heavy load.  This is worth double-checking.  There are many VMWare articles on this and it is a bit confusing.

We have seen major performance improvements with the new hardware (8-core, dual processors) and SAN attached storage instead of direct attach.  Which are you using?

One final thought - our performance team complains that they cannot get good data on VM's due to time drift.  This is an obvious problem if you want to measure performance.  Is this still an issue on the latest flavor?

Regards, 

Greg Askew 

Perhaps, but most of the benefits of VMware and DR can be achieved by using Ardence and since Presentation Server is already fault tolerant why spend/waste the money on feature like HA?

How so?  That is a very ingnorant statement...  ESX is suited only for a handful of implementations as there are better virtualization techniques that will yield the same benefits.   If you wish to save a tree, don't use ESX and you will end up using less hardware for a typical citrix deployment than you would with the ESX tax.

We saw similar performance (15 users per server) with a VSMP dual-processor virtual machine configuration. We found a single processor VM performed much better (40 users per server) than the dual. IIRC, monitoring showed the dual-processor VCPU %Ready stats were very high; indicating the dual-processor VM was ready to process, but the host could not allocate available CPU.

In this particular case, we had an application that required local deployment at remote sites and 40 users per server was sufficient to run the application. We did not consider converting the centralized farm of 1500 users to VM because we could get 60+ users on a physical server.

Vincent Vlieghe also created some nice guidelines. Always usefull when you consider running CTX/TS within a VM

http://virtrix.blogspot.com/2007/03/vmware-best-practices-for-deploying.html

Use Xensource with Presentation Server?

Has anyone tried?

This will be the challenge for Citrix. I am sure Citrix tested PS on Xen before the purchase.

There has to be more to this purchase than Citrix is admitting.

Citrix will make 50M in revenues from Xen next year? They would have been better off investing 500M for a 10% return each year. Better yet - they should have jumped on the VMWare IPO for a 100million return already. I know there is something we are all missing.

Works like a champ!  Just watch out for drive remappings.

In fact, I hear more and more Citrix customers are looking at XenSource now rather than VMware.  :)

Xen working with PS is one thing but how is the performance compared to VMWare.

I am sure more Citrix customers will be experimenting with Xen but we need performance comparisons from a non-biased source.

The limitation with the scheduler and vSMP did not change.. With 2 vCPUs you need to have 2 logical Processors free in order to schedule a thread.. Stupid if you ask me, but that is the limiting factor as appies to both versions.  The reason people think it's better in VI3 is because the new hosts have 2 and 4 core CPUs thus giving ESX more opportunities to schedule (have 2 processors in a READY state)

I think it really comes out depending on your environment. I have an old Dell PE2600 dual 2.4 Xeon, 3GB, ESX 3.0.2, with 4 VMs running on it with one being a PS4.5

 This PS VM server has 20 concurrent users and is working like a charm

PS4.5 VM config : 1.2Gb RAM, 1 vCPU and VMDK on a CX3-20 Raid 5 LUN

On the other VMs I have a Domain controller, Printer Server (All business apps prints goes through it) and McAfee ePo server

Perf stats:

CPU constantly less than 50% with some pikes during backup time frame 

RAM using 2GB out of the 3GB

So again, for some, using TS or citrix in a VM is very interesting. i have a copy of the VMDK and i can swap it at any time since on this server nothing is saved as i have a seperate file server (in a VM) 

As I understand VMWare suggests VI3 AND QUAD core cpu's for Citricx PS. I do not know (no experience) if QUAD core CPU's have the same problem (X2) as DUAL cores.

Anyone???? 

bit of a vague statement, any reasons why? pro's & con's. have you had experience using both?

We have a client with 3 Vmware 2.0 Servers, hosting over 900 Citrix Users on a poorly designed San, (Raid 5)Quad x Dual Core cpu's, And Performance Rocks. over 30-40 Users per server- no problem.

Now with VI 3.0, we are pushinc the boundry even more. We have a different customer with a hard core limit of 22-23 users per Physical server. No mater how many cores. With VI3, on Same server, but upgrade of ram-, We are able to 6x the amount of users per physical server. IE 6 VM's 21-23 uers per VMCTX server. There are places this works, but it needs to be tested, / tested/ tested. for full capability. With todays new procs.. i can envision much more density..

ALSO as a note.. RULE of thumb.. OVerload the ESX server With NICS!!!.. In my analysis, with CitrixVM's,, the amount of packets flowing from a ESX server climb way past 5000 packets per second. I have nt ran into issues with user limititations, except, when i under load the servers with network connectivity. Then it starts to suffer quickly. Nics seem to have been the cluprit in most of my installs.. 

There is a diference between Published Application and Remote Desktop, We were using a complete citrix enviroment (Remote Desktop) citrix 4.5 and then evaluated ESX 3.0 togather with citrix. We found citrix works well in an ESX enviroment slightly less users per box than a hardware solution (to be expected). ESX excels as a backup/DR solution or for sandboxing / underutilized servers however if your citrix enviroment is allready on limit ESX will not be a solution. In the end we went for a hybrid Physical Citrix servers with back up on the ESX farm, several under underutilized servers also on the ESX farm then we virtulized everything DC's Mail, DB's file servers etc... this proved to be the best solution reducing the number of physical machines but not performance. during a disaster recovery we would have less preformance for sure, but it is allways available. Hope to have been of asistance in this complex question.

XenServer (and Xen) doesn't have a host OS -- it is every bit as much a bare metal hypervisor as ESX.  It does its I/O via a fast memory-mapped channel to the control domain instead of a fast memory-mapped channel to a vmkernel -- bit the path is the same length, and the architecture is as bare-metal.

(And on the other point: use of hardware assist for Windows is NOT like VMware's emulation. Hardware assist is actually much more like paravirtualization in its simplicity -- the only reason it does not yet show speedups over VMware emulation is that the hardware assist cycle counts are high.  As each generation of new silicon brings reduced cycle counts, the advantages of the approach should rival those of paravirtualization.)

So does that mean you can run XEN without Linux?   That's amazing!   Where do the device drivers come from?  OpenSource? Is there a certification programme for XEN drivers?   Does a driver certified for Citrix XENServer mean it's certified for Novell XEN, Oracle VM (XEN), Redhat (XEN), Virtual Iron (XEN)?   Does the same VM work across all these XEN variants without change?   If I need to change the VM, what else is different between all these variants?   Are all the commercial XEN distributions handing back their IP to make XEN better?  Or have they forked XEN, to compete against each other and retain a competitive advantage?   The fast memory mapped channel to the control domain sounds great, what is the control domain? If XEN is bare metal, where does the Control Domain sit?   Could it possibly be that the Control Domain is actual Linux and therefore all I/O is going through this domain and through Linux device drivers that are installed here, if Linux is installed, and it's loading the device drivers to talk to the underlying hardware, then surely XEN is sitting on top of Linux?   hmmmmmm   I'm now confused....    Seems the architecture isn't quite the same.... If that's not the same, then may be there's some performance, reliability and security benefits of certifying drivers for virtualisation, removing the extraneous code, optimizing them for a virtual world and putting them directly in the kernel and putting that kernel on the baremetal without another operating system to help it along.  Getting rid of that management VM (Service Console) was the best thing VMware did, I got fed up with all those Linux Security patches we had to deploy, wonder if that control domain XEN has will have to be patched as often?  I guess only time will tell....    I wonder if Microsoft adopted a similar model for HyperV.... oh that's right they did.... hmmm their Control Domain must be huge, that's going to be fun on patch tuesday.