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March 28, 2012

Optimizing Virtualized XenApp with Atlantis ILIO

Jim Moyle - Atlantis


Download the Shawn Bass Report on Atlantis ILIO for Xenapp

Behind the loud noise that VDI and consumerisation are making, there has been a much quieter revolution in the XenApp world.

There are two main drivers for this change. The first is the desire of the enterprise to have a consistent look and feel across the desktop, whether physical or virtual.  As the users’ physical desktop gets upgraded to Windows 7, they want the XenApp desktop to reflect this.  To get a Windows 7 look and feel with XenApp, requires an upgrade to Server 2008 R2 as the hosting platform.  The second is that the current implementations of XenApp are coming up to end of life.  Citrix currently support XenApp 4.5 to 6.5. These versions of XenApp cross many OS and architecture boundaries and must be very costly to support. By the 16th of July 2013, the ONLY supported edition will be XenApp 6.5.  As XenApp 6.5 is only supported on Server 2008 R2, these two different drivers are pushing customers towards a single platform to the enterprise.

Customers know that they must move to XenApp 6.5 on Server 2008 R2. As we now live in a virtual world, these servers will be virtualised by rule and physical by exception.  If we look a little closer at what is happening, it means a large number of enterprises will be moving from a physical XenApp 4.5 on 2003 x 86 infrastructures to a virtual XenApp 6.5 on 2008 R2 x64 infrastructure.  This has a large impact on many desktop considerations.  There will likely be a move to Office 2010 along with a move to IE 8 or 9 and more use will be made of application virtualisation.

There is a huge difference between a desktop and a server workload and that difference is interactivity.  Every keystroke and mouse move has a consequence.  The user needs to interact with the desktop in a consistent, fast and predictable way.  The way that Windows deals with this is its ability to consume resources on demand. You can easily see this if you run performance monitor and measure CPU, memory and storage counters while opening an application. The resources that Windows consume suddenly burst upwards.  These bursts are characteristic of a desktop workload.

If we realise that the resource burst is necessary to the desktop, it means that sizing becomes more problematic.  If we size on average it means that 50% of the time our users will have a degraded experience.  This is obviously not acceptable.  We need to provide the correct amount of resource to allow a consistent user experience.  CPU and Memory concerns are relatively easy accomodate for two reasons:  the risk is confined to a single host, it is impossible for a problem on one host to directly affect the others and hypervisors provide good quality of service features to ensure no VM consumes too much resource.  Storage, on the other hand, is a different story.  Not only is it the most bursty of all resource consumption, it is shared between hosts making the risk of failure much higher.

Atlantis Computing can eliminate up to 90% of the IO coming from the virtual desktop images.  The new release of Atlantis ILIO for XenApp extends storage optimization to virtualized Citrix XenApp deployments. Using Atlantis ILIO for Citrix XenApp will reduce provisioning time, accelerate boot times, deliver a consistent user experience, increase density and require up to 90% less storage for XenApp.

Atlantis ILIO for XenApp

The ideal architecture is to place an Atlantis ILIO virtual machine on each server with the XenApp virtual servers.  This means that the IO from Windows Server 2008 R2 is serviced within the hypervisor of each host using Atlantis ILIO to offload IO from the storage system and avoid performance issues cause by storage latency .  By optimising the I/O generated by the XenApp servers, Atlantis ILIO provides a large amount of low latency IOPS that gives the desktops the ability to consume storage on demand and provides the headroom for the desktops to burst into.

Atlantis Computing asked one of the longest serving CTPs, Shawn Bass to test the benefits of using Atlantis ILIO with XenApp.  

The full detail of Shawn’s testing can be found at  The summary of the testing is as follows:

Atlantis ILIO Test Results


  • Provisioning – 53% faster provisioning
  • Boot Time – 4x faster boot times
  • Applications – accelerates response time of IO bound applications


  • Server Density – 16% increase in users per server
  • Storage Density – 10x more users on existing storage

Storage Savings

  • Storage Capacity  – reduce storage capacity by 92%
  • IO Offload – reduce IO to storage by up to 90%
  • Latency – reduce IO latency to improve response time

As you can see if you, along with the rest of your peers are going to be using XenApp 6.5, you can make a huge difference to your XenApp deployment by employing Atlantis ILIO for Citrix XenApp.

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