VDI's Impact on Network Infrastructure

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It's been clear for some time that the initial rosy ROI projections surrounding Virtual Desktop Infrastructure (VDI) didn't exactly tell the whole story.

While it's true that a strict comparison of the cost of virtual clients versus traditional desktops showed dramatic savings, expanding the view to include the impact on storage produces more sobering results. But even after you factor in the cost of additional storage, you're still only getting half the picture. Equally troubling are the network upgrades that come into play.

Indeed, I/O latency is seen as one of the major limiting factors in VDI performance, and the problem only gets worse as more seats are added to the mix. At a minimum, VDI will require near-universal 10 Gbps connectivity, but as The Register's Robin Birtstone points out, that may be only the beginning. Since most SANs are built around relatively low-latency server access, an upgrade to high-performance, and high-cost, Fibre Channel is probably in order. At best, a hybrid environment featuring a mix of FC, FCoE and iSCSI might work, but again, you have to factor in the considerable cost of new Converged Network Adapters (CNAs).

For those who think VDI is simply an expansion of the virtualization taking place in the server farm, The Taneja Group's Dave Bartoletti has some bad news. The fact is that VDI is only cost-effective at much higher densities than server virtualization. But because desktop workloads are so spiky, you end up deploying much higher sustained aggregate I/O capability, further eating into the return on that initial VDI investment.

Practical experience is also turning up a number of unanticipated problems with VDI. Tech consultant Paul Robinson notes that many NAS architectures don't have front-end Windows capability, locking out links stored on non-Windows platforms. And while most server architectures can get by with a pair of 1 Gbps network cards, suddenly adding multiple desktops, each requiring its own 1 Gbps link, will quickly overload most systems.

In typical fashion, however, one person's dilemma is another's opportunity, and there certainly is no shortage of solutions bent on solving the VDI connectivity problem. One of the latest is Virsto, which has tweaked its VM management engine to address the higher density VDI environment. The company says its thin-provisioned virtual disk technology can cut deployment costs nearly in half and reduce capacity requirements some 90 percent, at a cost of about $2,800 per host.

Supporters hail VDI as a disruptive technology that will change the way the enterprise functions. Disruption, though, is only useful if it leads to an improved state of being. Advanced management techniques notwithstanding, VDI exacts a high price while still providing only vague promises of a better future.

To be fair, many of the network upgrades mentioned above are happening independent of VDI as enterprises bolster their infrastructures in preparation for advanced cloud architectures. In that vein, then, VDI will likely get its foot in the door one way or another but only as an afterthought -- not a bold new direction in data functionality.