There is currently a massive install base of customers running Citrix XenApp 4.5 with Windows Server 2003 that need to move to Citrix XenApp 6.5 with Server 2008 R2 before support ends in March 2013, according to Vincent Branger, virtualisation expert and consultant at Infralys.

Meanwhile, many existing deployments of XenApp are still on physical hardware, so organisations are planning to virtualise their servers at the same time as migrating.

However, the combination of virtualising XenApp and moving to Windows Server 2008 requires a significant increase in the amount of shared storage needed to avoid performance issues. This is because virtualising XenApp causes a storage bottleneck that increases provisioning times, extends boot times and can reduce the number of XenApp sessions per server.

Atlantis claims that ILIO for Citrix XenApp continuously optimises the storage traffic of the virtualised Windows Server throughout the daily cycle of re-provisioning, bootup and logon, reducing the amount of storage required by up to 90 percent and speeding up provisioning by 53 percent.

"Both VDI and Citrix XenApp/RDS follow patterns of approximately 80-90 percent write activity vs. read activity during steady state," explained Shawn Bass, Citrix CTP and Microsoft MVP. "Deploying RDS/XenApp workloads behind Atlantis ILIO can reduce storage requirements, improve provisioning and boot time and improve scalability."