The efficiencies and cost savings of a virtual desktop architecture are clear. What many business customers don’t realize, however, is that the usefulness of their virtual desktop setup strongly depends on the data center arrangement of the cloud solutions provider they choose.
The chances of a good quality of experience (QoE) are greatly improved when cloud providers use a distributed data center architecture, according to a recent Alcatel-Lucent (News 
- Alert) white paper, Virtual Desktop Performance And Quality of Experience.
Cloud providers with a distributed data center have an advantage over centralized data centers when it comes to virtual desktop architecture. This is because bandwidth is not the only factor that affects QoE. In fact, latency plays a big role in user satisfaction, the Alcatel-Lucent study found, with network delays of more than 40ms creating a perceptible difference in QoE. And, reality is that with centralized cloud environments, delays longer than 40ms are common.
“Latency for centralized data centers varies depending on the user’s location and the number of service providers between the user and the serving data center,” Alcatel-Lucent says. Latencies of 40ms to 120ms are not uncommon when the connection to the serving data center traverses regions.”
Not that bandwidth doesn’t also play a large role when a virtual desktop pulls from the cloud.
Although virtual desktops require minimal network conditions, QoE and a user’s willingness to pay for a virtual desktop drops dramatically if there is a guaranteed bandwidth of less than 6 Mb/s, according to the paper. It states that this is the minimum amount needed for users to feel that virtual desktops perform like their non-virtual desktop counterparts.
The impact of this becomes apparent particularly with video. Alcatel-Lucent found that video QoE is more dependent on bandwidth of 6 Mb/s or above, and that a quality video experience drives a user’s willingness to pay for a virtual desktop experience.
The impact of bandwidth
Bandwidth cannot be over-emphasized as a key driver in user QoE. The paper states that Alcatel-Lucent found that bandwidth falls in a consistent slope as roundtrip latency increases from 20ms to 120ms. This means a cloud provider’s use of a distributed data center over a centralized one must be a key consideration for companies using or planning to use a virtual desktop architecture.
Network and IT-related factors also impact QoE when it comes to a virtual desktop environment. These include:
- Network jitter
- Choice of VDI transport layer protocols (RDP, RGS or PCoIP)
- Dynamic behavior of multiple desktops on the same network
- Virtual Machine configuration
- Storage performance in case of desktop boot storms
- Data center network performance
With latency being an important factor, the paper says that communications service providers are in a particularly good position to build distributed data centers and become important players in the virtualization market. A 2011 Alcatel-Lucent study found that trust is one of the most important enterprise factors when choosing a cloud provider and that trust is based on assuring a QoE that is reliable and measurable. In other words, a distributed data center offering can enable communications service providers the competitive edge they are desire in a market that is critical to their futures as well as those of the customers they seek to serve.
Edited by
Peter Bernstein
