Technical Deep Dive: XenApp Load Evaluators

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One of the often overlooked features of XenApp is truly understanding the load evaluators. As a consultant, I commonly see environments using only the Default Load Evaluator. If I am lucky, they might be using the Advanced Load Evaluator. Rarely do I find organizations actively monitoring or customizing their load evaluators.

Load Evaluators have not changed much since Presentation Server days, but amazingly they are not commonly optimized. Every environment and every workload is different, so whichever load evaluator is implemented may vary, but they should be customized and monitored.

Are you ready for VDI?

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More companies are investigating the benefits of implementing a Virtual Desktop Infrastructure (VDI).  If you are one of those companies then you need to ask yourself, “Am I ready for VDI?”  The first step is identifying exactly what VDI means to your organization.  VDI actually encompasses several types of delivery, but is most commonly associated with what Gartner classifies as hosted virtual desktops (HVD).  VDI can also include implementations of server-based computing (SBC), hosted shared desktops (HSD) and client-side virtualization.  For the sake of simplicity, we will focus on the hosted virtual desktop model for VDI since that is the most common assumption of a VDI deployment.

Citrix Synergy 2011

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If you are thinking about going to Synergy this year, I will be assisting in moderating the XenClient learning labs (SYN409D) during Summit and speaking as part of the XenDesktop team during Synergy. This is an exciting opportunity for me! If you are planning on attending, check out the 5 part WOW TO HOW Series, I will be speaking on Part 3: Storage Infrastructure (SYN305)

For more information on Synergy, or to register, follow this link: Synergy 2011

To see more details on my session, follow this link: SYN305

Joining GlassHouse Technologies!

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I'm happy to announce that I have joined the team at GlassHouse Technologies as a Senior Virtualization Consultant. With this role, I will be tasked with helping manage virtualization projects, with a main focus on Citrix Technologies.

My main focus will be on expanding our XenDesktop / Virtual Desktop offerings, and will leverage all of our corporate expertise on Datacenter Management, Virtualization, Storage and Security.

Citrix closes the gap with VMWare -- XenServer 5.6 Beta, Part 1

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Most of the complaints I've heard in regards to XenServer vs. VMWare is the fact that XenServer does not allow an overcommitment of memory.  If you have a host server with 16 GB of RAM, you can only allocate up to 16 GB of RAM for the guests (yes, I know, technically less since Xen requires some resources... but you get the point).

Personally, I'm not a fan of over-allocating memory.  I actually like that with XenServer, I do not have to worry about it.  I've seen too many VMWare farms suffer because of assigning too much memory then having to constantly swap resources.  I think if you engineer the solution correctly, and size your servers properly, memory allocation should be kept in check.

However, seeing this as a fault when comparing virtualization host platforms, Citrix has released the latest Beta of XenServer 5.6.  One of the new features IS allowing your to over-allocate memory... they call it Dynamic Memory Control.  I have to admit, it is pretty cool and very easy to use.  The XenCenter display makes it VERY intuitive... all the better to see WHERE your resources are allocated, especially when squeezing memory.

 
To read more technical details, see my full article at: http://www.thegenerationv.com/2010/04/xenserver-56-preview-part-1-dynamic.html

Direct Booting a VHD in XenServer

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I've run across several instances where I needed to direct boot a VHD in XenServer.  One example was migrating from Hyper-V to XenServer.  Another was updating the network stack, XenTools, and PVS Tools on existing vDisks.  Regardless, the following is the three-step process I took...

Recovering from XenServer Root Drive Full -- Oppsie!

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I was trying to import a VHD straight into XenServer the other day. I was moving a VM from HyperV to XenServer 5.5, so instead of starting from scratch, I thought I would simply copy the VHD from HyperV to XS using WinSCP. Following the directions from Trevor Mansell's Citrix Blog

All went well until my XenServer died on me...

The Future of Computing? BYOC!

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Check out my latest article, and in depth look at Bring Your Own Computer to Work Policies...

A growing trend in technology firms is Bring Your Own Computer (BYOC or BYOPC). Of course organizations such as Microsoft, Google, Citrix and Cisco are embracing this -- which is to be expected. However, as workforces become increasingly mobile, and virtualization methodologies are further adapted in enterprises, BYOC will inevitably grow.

Deploying Windows 7 with XenDesktop 3

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I've been running Windows 7 since May. I have to say, I've very impressed. Microsoft got it right. They took the best of XP and Vista (and MACs), plus some good common sense features to make a great product. I've run it on three systems, ranging from a brand new Quad-Core 4gb RAM laptop to an old single-core 1gb ram nc6120.

As a virtualization engineer, I'm seeing a lot of customers evaluating virtual desktop deployments as a way to distribute Windows 7 in their enterprise. It would be easy to argue Windows 7 is a reason they are embracing VDI; of course, it is just as easy to say they are using Windows 7 as the excuse for VDI. Either way, both are gathering steam.

Windows NLB on Hyper-V R2

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Today I had the luxury of setting up a Unicast NLB on a couple of Windows 2008 servers (for Citrix Web Interface 5.2). The servers themselves are guest VMs running on Hyper-V R2. I noticed that when trying to create the NLB, it would not converge. The NLB wizard was erroring out, plus the entire NIC would go offline, losing its static IP association. I would also see Error 12289.

Optimizing XenApp on VMWare ESX

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There are numerous benefits for running Citrix XenApp on XenServer; including single vendor support, built-in optimizations, and integration features. However, what if you are working in a VMWare ESX environment? As a consultant or an internal engineer, you cannot always dictate the virtualization environment. The following are some tried and true best practices for optimizing XenApp on VMWare ESX.

Read More, view the full article at GenV: http://www.thegenerationv.com/2009/10/optimizing-xenapp-on-vmware-esx.html

TheGenerationV.com

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I'm happy to announce that I am joining the team over at TheGenerationV.com.

I will still be maintaining my personal blog here as time allows, of course, but will also be writing case studies and analysis articles for GenerationV.

TheGenerationV.com is dedicated to hosting discussions and technical articles about next generation technology. TheGenerationV.com was founded on July 10, 2009 by Rick Rohne, however, it is made up of some of the most talented Systems Integrators in the country.

I'm looking forward to sharing my thoughts on virtualization with this team of engineers. Please come check it out.

Louisville-Area Citrix Users Group

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Chris Morgan with University of Louisville School of Dentistry has started a Louisville-Area Citrix Users Group. He and I had been discussing this for months with our regional Citrix sales management team. I'm glad to say he has taken the initiative and created a MeetUp site to facilitate this new group.

If you are a Citrix user, administrator or engineer; using Presentation Server, XenApp, XenServer, XenDesktop, NetScaler, or any other Citrix Technologies; or if you are interested in learning more, please sign up at http://www.meetup.com/citrixlouisville/

Also, as new group, we are looking for topic suggestions and vendor sponsorships. Feel free to submit any ideas you may have.

Now With MTM!

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I'm ecstatic to announce I have joined the team at MTM Techonologies as a Systems Consultant. I had the pleasure of working with MTM as a customer for many years. During this time, I had the opportunity to get to know them top to bottom. When the time came for me to make a change, this is the team I knew I wanted to join.

Quest vWorkspace

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Some time back, Quest Software purchased Provision Networks. They have sense re-branded and re-released their Virtual Access Suite (VAS) product line as vWorkspace.

Latest and Greatest: My Citrix on VMWare

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This may be my last entry on Citrix/VMWare for the time being.

After 1 month of production runs, our 1 vCPU 2GB RAM VMs are churning nicely, averaging around 32 concurrent users. Running at 10 VMs per DELL 2950 Host, we see that Host Memory is stable, Host CPU is well utilized. There is enough capacity that another 2 VMs could potentially be added with no adverse effects, netting approx 380 users per HOST... solid density.

More on Citrix Load Evaluators

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Well, most of feed back I received from other industry players confirmed my initial suspicions... counters based on Windows Perf Counters where Windows is a VM are not reliable. A local area architect, who is not married to any one technology, summed it up nicely:

"You have touched on something that is inherent to the virtual world: the performance counters are always wrong. Exactly how wrong, that is debatable. In the past, I have used empirical numbers to control load. That means keying off of something like user count, memory utilization, or page swaps. It isn't an exact science, but some testing should give you the right mix."

Citrix Load Evaluator Rules in a VM

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I mentioned in my previous post that one of my VMs was pegging at 100% of the vCPU, but the Windows Task Manager was showing only spikes (although a lot of them), and my Citrix load value for that server was in the 7200 range. Of course, the system was crawling and unusable for customers.

Update on My Citrix VMWare Machines

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Ok, if you have been following my blog, you know I have been researching and building the best possible Citrix VMs to run on my ESX Hosts. Granted, XenServer might be better for XenApp, but we work with what we have, and I have ESX 3.5.

I currently have 4 production VMs running, 2 in each production Zone. The first two in DataCenter1 went live about a month ago... and churn nicely. They will routinely show a load evaluation of 10000 (Full Load), and the 1 vCPU Utilization is fairly high (based on vCenter stats), but no complaints from users. Initial test = PASS.

Citrix on VMWare ESX

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Although these guidelines are created using the following environment, these standards should apply to just about any Terminal Services-based virtual environment (XenApp 5, Quest vWorkspace 6, 2X, Windows 2008 TS, etc.):

• VMWare ESX 3.5 Update 2
• Virtual Center 2.5
• Windows 2003 R2 SP2 Standard Edition
• Citrix Presentation/XenApp Server 4.5