Citrix VDI: Distributed Computing 2.0
Distributed computing has dominated IT architecture for nearly 20 years. From early notions of client server computing, IT has needed to implement significant changes in the infrastructure required to support the way that users access applications, which have been rapidly growing in complexity. The most dramatic changes, however, are yet to come. The real revolution in distributed computing starts with the adoption of hosted virtual desktops. In a hosted desktop scenario, IT centralizes the running of PC operating systems and applications on virtual machines (VMs) hosted on servers in the data center while streaming a display protocol to a light-weight client application that can be run on various devices on the network.
Desktop virtualization builds on the notions of server virtualization, which utilizes a physical server to host multiple virtual machines that run their own server-class OS and applications, which are typically in the form of backend services. In a desktop virtualization scenario, however, the hosted desktop VMs need to support a highly GUI-centric environment running interactive client applications. As a result, a virtual desktop infrastructure (VDI) introduces a number of new specialized technologies—from session brokering to display streaming—for IT administrators to support.
In a traditional PC environment, resolving configuration management and problem remediation issues requires IT administrators to attend to physical clients individually. This situation dramatically drives up the cost of IT operations associated with hardware and software provisioning and maintenance. As a result, centralizing virtual PC operations in a datacenter with hosted desktop VMs, applications, and data all residing securely on servers in the datacenter should make managing and securing desktops significantly easier for IT. To fully leverage such a scheme, even more advanced VDI solution are needed to address such issues as virtual desktop provisioning and the streaming of PC applications and disk images.
In terms of today’s $150 billion worldwide market in business PCs, Gartner pegs client systems deployed on VMs to be around 500,000—about the level of a rounding error. Nonetheless, as IT finds it conceptually easy to leverage existing infrastructure to offset VDI entry costs, Gartner projects the percent of new business PCs being deployed on VMs to rapidly rise to 40%. According to Gartner, IT in the US will lead this trend by migrating 30 percent of their installed base of desktop PCs to VMs by 2014. At that rate, the ranks of VMs running client systems will swell to over 18 million.
That rosy scenario for VDI is not without its dark side. In a survey of CIOs implementing server virtualization, IDG reported that the percent of CIOs saying that datacenter management had become more complex rose from 47 percent at the end of 2008 to 67 percent. That increase in perceived complexity raises a serious red flag for VDI, as best practices call for deploying desktop VMs four to eight times more densely than server VMs. What makes dense deployment plausible is the sporadic nature of desktop PC usage. While dense VM deployment enhances the potential for significant cost savings, dense deployment also increases the need for IT to be prepared for resource-utilization storms involving I/O, memory, and CPU resources.
A pivotal resource for making the transition to server and desktop virtualization is a SAN-based storage infrastructure that scales out in capacity and performance. The inextricable links that storage resources have to the capital and operational expenses that IT must restructure to maximize the return on investment (ROI) of any virtualization or consolidation initiative continue to make optimized storage a critical success factor.
