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Implementation Challenges with VDI

October 28, 2011

There are a few challenging technical areas that every VDI environment must overcome at some point. Although the installation of VMware View components is very easy, there are some areas of design that need attention and may pose a challenge. The challenge level will depend on the environment and infrastructure you support.

Storage I/O: Storage is at the heart of server virtualization and it’s no different for VDI. When you centralize virtual desktops everything that occurs without VDI is compounded and can stress the storage infrastructure. I/O storms can occur from simple things like user login, boot up, and shutdown. For example, virus scan software, which could be configured to run on each virtual desktop, may use the same policy as physical desktops, and scans are commonly scheduled at the same time; scans are very I/O intensive. User experience will degrade quickly if the storage subsystem can’t handle peak I/O requirements. VMware recommends in their Performance and Best Practices white paper to use solid-state drives (SSD) for replicas and spinning media for the other virtual disks for best performance. Storage arrays that take advantage of SSD can support upwards of 80,000 IOPS if done correctly. If you’re using a network protocol for storage, jumbo frames, an isolated network and plenty of bandwidth to the storage array can make a difference.

Wide Area Network (WAN) issues: The WAN itself is not the challenge; the culprit is low bandwidth and high latency. Bandwidth is not cheap and lots of things are riding the WAN back to the data center, where in most cases the VDI environment is also located. So the challenge is sizing the WAN to accommodate the added bandwidth for VDI. In some cases, there is a drop in WAN utilization with virtual desktops in the data center with the core applications. You won’t know for sure, so plan for the increase. In the white paper reference above and using PC-over-IP (PCoIP), VMware claims a 75 percent bandwidth reduction can be achieved. A WAN optimization product like a Riverbed Steelhead appliance can also work well.

Other not-so-technical areas can also make deploying VDI challenging. I’ve made a list below, which is by no means comprehensive:

  • Licensing:  Unfortunately, an unavoidable hurdle. While Microsoft has improved their licensing around virtualized environments, the OS still comes with a cost.
  • Solution details:  No one solution has synergy across the top three desktop OSes (Windows, Mac OS, and Linux). You must decide which combination of solutions will give you the most bang for your buck, based on your requirements.
  • Upfront cost: Typically, upfront costs for building a VDI environment are high. This can deter companies from deploying VDI, especially in this economy, and when ROI is hard to identify.

Every company will have different challenges. A good VDI environment can offer agility for desktop services and applications, better security and compliance, standardization, and better management. Hurdles can be overcome by planning and putting the right solutions in place. Account for peak I/O loads and bandwidth utilization, because it will have a significant impact on user experience. Also, make sure to follow vendor best practices.


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