Tip

Ensuring XenApp scalability with resource allocation, load testing

One of the most important aspects of deploying a Citrix XenApp environment is scalability, whether it's planning for a new infrastructure or even upgrading an existing one.

From MetaFrame 1.8 up to today's XenApp 6.5

    Requires Free Membership to View

, Citrix Systems Inc. has made it a priority for XenApp to be able to scale the host environment out and up when needed. Expected to be announced at the vendor's Synergy conference in 2013, the two sub-projects under Citrix's Project Avalon, Excalibur and Merlin, could include even more scalability features and architecture.

There are a couple of different ways to ensure XenApp scalability. First, you need to pay attention to the design of the virtual infrastructure that will be hosting the environment, specifically the amount of RAM available to all virtual machines, the amount of overall CPU processing power available, and the size, connectivity speed, and type of disk storage that will host the virtual disks and files. Plan for what you need today, add what you might need tomorrow, and then add 20%.

How resource allocation affects XenApp scalability

One tactic many shops use to guarantee scalability is over-architecting the virtual host environment to allow for future growth without having to purchase additional hardware. If you don't supply enough resources, bottlenecks in your XenApp environment can have a huge impact on its ability to scale. Disk, CPU, RAM, or network congestion inhibit the ability to expand a farm to accommodate more users, hosted applications or hosted desktops.

Some of Citrix's documentation on XenApp scalability factors do not seem to fit with the situations I've encountered in the real world. For example, this Citrix blog points out that CPU is "always" the primary bottleneck for XenApp 6.5. However, I have seen more times than I can count that disk I/O has been the primary bottleneck, especially with Hosted Shared Desktops or XenDesktop implementations.

RAM is a close second (sometimes first), with CPU actually being the last resource that causes bottlenecks. The post's author does not explain his testing scenarios, so I can't compare them truly one-for-one with my experiences.

Using load testing to allow for XenApp scalability

One of the primary things you can do to create some really good scalability baselines with XenApp is to employ a load-testing methodology.

More on Citrix XenApp

Comparing XenApp with App-V and ThinApp

Tools for WAN optimization in XenApp

XenApp vs. XenDesktop

You want to create a load-testing scenario that comes as close as possible to real-world user application and desktop usage in your environment. If you can use live test users, that is a huge plus because it offers a more "true" test and adds flexibility to your load testing with things like latency logins and different endpoints. Still, it does require extra work in coordinating the testing and making sure everyone is testing what they should.

Citrix provides an automated load-testing tool, as do many other vendors, that will generate load on XenApp and run that load for as long as you want. You create a testing scenario with user logins, application launches and use, and all the data on the XenApp environment performance is recorded for further analysis. With the automated load testing, you do lose some flexibility that you have with manual testing, but it doesn't require as much in the way of resources or tester coordination.

Citrix has published the Design and Scalability Considerations for Enterprise XenApp Deployments white paper, but it does not directly address the impact of scalability on Hosted Desktops or XenDesktop implementations. Here are other options for further reading to get you started:

This was first published in March 2013

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to:

Expert Discussion

Which factor do you find causes the most bottlenecks in a XenApp environment?

Mike Nelson
What's your opinion?
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Disclaimer: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.