The utopian vision of a fluid and easily managed desktop infrastructure has floated around IT since the dawn of the desktop era. There have been many attempts at corralling the desktop hydra, but none have provided a universal solution. Microsoft Terminal Services, Citrix XenApp, and a host of others have found markets, but the quest for desktop salvation continues.
Enter the newest comer: VDI (virtual desktop infrastructure).
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At its simplest, VDI is nothing more than one desktop VM per user, running on top of a hypervisor. As with server virtualization, each desktop VM is assigned RAM, disk, and I/O resources, and a full installation of the OS resides on the virtual disk. The user interacts with the desktop VM using a remote display protocol such as Microsoft's RDP (Remote Desktop Protocol) or Citrix's ICA (Independent Computing Architecture). The client is generally a diskless, power-sipping, thin client system that does little or nothing more than connect to the VDI infrastructure.
The result of this and other server-based desktop computing solutions is that the core of the functionality -- and all the precious company data -- is contained within the data center, not spread far and wide among cubicle farms or across many miles to remote sites.
By centralizing desktops, you simplify administration and security and remove the need for such basic desktop maintenance as replacing failing power supplies, hard drives, and so forth. Power consumption is also reduced, and in some cases, cooling costs for dense office spaces drop due to the removal of all those fat client systems and their 350-watt power supplies. The upside can be substantial.
Devils in the VDI details
But there are definite downsides to VDI. Some of these issues are found in other server-based desktop computing solutions but affect VDI implementations as well.
Let's start with the most important issue of all: user acceptance and overall performance. Each VDI instance may be fast and snappy while performing relatively mundane tasks like word processing, emailing, or running spreadsheet formulas, but they can suffer mightily when confronted with rich content like Flash applications, videos, or other multimedia applications. This is generally due to the desktop display transport protocol rather than the performance of the VM, but that only makes the problem harder to solve. Very public problems may arise with user acceptance, which is generally the death knell of any large project.