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March 27, 2014

Benefits of Virtualising Citrix XenApp with Atlantis ILIO and IBM Technology

Andrew Wood - Atlantis


Why should you virtualise Session Host based workloads such as Citrix XenApp? What are common pitfalls? How can these be addressed with Atlantis ILIO and IBM technologies?

In the first part of this series, Benefits of Virutalizing Citrix XenApp, we discussed benefits of virtualizing Session Host based workloads. To summarise, the advantages of virtualizing a Citrix XenApp environment were:

  • Accelerate desktop and application performance
  • Increase server utilization and density to decrease TCO
  • Simplified maintenance through abstraction and automation
  • Smaller failure domain and simplified disaster recovery
  • Faster deployment and migration either to XenApp 6.5 and Windows Server 2008 R2 or beyond.

While there are significant advantages, it is best to be aware of risks to successful delivery:

  • Storage challenges: When XenApp is virtualized using SAN or NAS-based storage the combination of IO blender, RAID overhead and network latencies can increase the cost of storage configurations required to meet application performance expectations. Increasingly, local SSD storage is considered to accommodate performance requirements. Yet, as discussed in Understanding Storage Performance Challenges in Virtual Desktop Environments the random, write-intensive nature of environments such as Citrix XenApp can cause premature SSD failures that increase OPEX costs. SSD capacity can also limit user densities in these environments, further increasing CAPEX costs.
  • Impact on Density: when moving to Microsoft Windows Server 2008 R2 or Windows Server 2012, it is important to know that Citrix XenApp running in these newer OSes can require almost double the number of IOPs for a given level of application performance from earlier Windows Server versions.
  • Performance issues: Provisioning, boot/logon time and I/O intensive operations will all be impacted by reduced storage performance. As new applications are deployed there is an increased demand on CPU capacity – optimising storage performance can free CPU cycles for improved application performance.
  • PVS Write Cache: Citrix XenApp is most commonly deployed using Citrix Provisioning Server (PVS). PVS requires storage for a write-cache. More than 50% of deployments are configured with a Write Cache size larger than 10GB per XenApp VM: this means the storage capacity required for a XenApp deployment can be expensive to deliver and support.

These risks can lead to cost overruns and project delays: impacting go-live dates and preventing business change. Poor performance can increase help desk call volume due to poor user experience, which in turn has business impact through reduced productivity.

In this blog, we’ll discuss the benefits of using Atlantis ILIO and IBM Technology to drive the best performance and density from your virtualized Citrix XenApp environment.

Advantages of Virtualised XenApp with Atlantis ILIO

By optimizing how storage is provided, Atlantis ILIO allows Citrix XenApp instances to be run at performance levels that far exceeds what traditional storage solutions can provide. Atlantis ILIO can operate in two modes to optimise virtual XenApp environments.

  • In-Memory: the Atlantis ILIO In-Memory architecture is designed to deliver the consistently high performance and low latency by using a server’s RAM as storage for virtualized XenApp (XA) servers. An In-Memory Atlantis ILIO appliance makes it possible to remove the requirement for network storage or SSDs: allowing for a simpler host architecture. By using de-duplication and compression technologies, Atlantis ILIO can neutralize the risks associated with Citrix Provisioning Service write cache growth by significantly reducing the SAN storage requirement. In addition, Atlantis ILIO offers the opportunity to leverage the performance of RAM as storage for Citrix Machine Creation Services (MCS), giving a flexibility of deployment options, without sacrificing performance.
  • Disk Backed: Atlantis ILIO can be deployed to optimise existing SAN/NAS/Flash Storage array or even local disk resource: key for those persistent XA servers delivering specific silo applications, or where the host server RAM is limited. By using de-duplication and content aware processing technologies, Atlantis ILIO can reduce the IOPS demand on existing SAN storage environments; improving the user experience while at the same time providing greater capacity and performance.

Atlantis commissioned Shawn Bass, Citrix CTP and Microsoft MVP, to produce a white-paper, Citrix XenApp & RDS Workload Improvements by Atlantis ILIO.

Such results were also experienced by the IBM Innovation Center who conducted extensive density, performance and scalability testing using industry standard benchmarking tools such as Login VSI v3.7 and IOMeter. Combining IBM Technology and Atlantis ILIO on a 2 x Intel Xeon X5650 with 256GB RAM delivered 200 XenApp user sessions for a single host. Importantly, performance testing showed the combined solution was 4.5x faster than the LoginVSI acceptable XenApp response time. Standard sizing guidelines often quote @10 IOPS per user session, the combined technologies delivered 242 IOPS per user.

Lab testing is one thing, but it is real world deployment experience that is most useful. It is interesting to view the experiences from Kelsey -Seybold Clinic, who wanted to ensure that their virtualised desktop and application environment has a “better than PC” performance. Kelsey -Seybold Clinic has approximately 3800 users and use Citrix XenApp to deliver their Electronic Medical Records (EMR) system (EPIC Hyperspace) to exam rooms for staff. Kelsey-Seybold Clinic chose IBM PureFlex as they found it the “sweetspot” for CPU processing power and memory density allowing rapid scale flexibility to the business needs. While they had a lot of tiers of enterprise-class IBM storage those tiers are shared amongst many applications the total amount of IOPS was very high and the footprint was very small. To drive the most cost effective use of the storage Atlantis ILIO was deployed to drive performance on each blade while putting all of our data onto IBM shared storage. For Kelsey -Seybold a key advantage of Atlantis ILIO was that it was a simple software appliance install that could be introduced with no changes to the existing infrastructure. By combining IBM and Atlantis ILIO technology Kelsey-Seybold can accommodate up to 400 users on a single host.

In the UK, a local government customer looked to ensure they could migrate from Windows XP. They used IBM System x3550 servers using Atlantis ILIO for XenApp for 90% of their 7000 seats with additional virtual desktops being delivered using XenDesktop. With the combined Atlantis/IBM solution there was a per seat saving of $45 over other options.

Benefits of Virtualizing Citrix XenApp with Atlantis ILIO and IBM Technology

Atlantis ILIO storage optimization technology fundamentally changes the economics and performance characteristics of VDI by intelligently optimizing how the Microsoft Windows operating system interacts with shared storage systems.

Deploying RDSH workloads such as Citrix XenApp on storage optimised by Atlantis ILIO can reduce storage requirements, improve provisioning and boot times and increase scalability when I/O is a limiting factor for scale. When combined with IBM PureFlex optimized organizations can deploy Citrix XenApp for virtual desktops with IBM v7000 or IBM FlashSystems storage for user profiles. As a growing number of IBM customers have found, this combination delivers a fantastic user experience and eliminates storage-related performance problems.

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