We (Sven Huisman, Jeroen van de Kamp and Ruben Spruijt) are pleased to announce the long awaited release of the Project Virtual Reality Check (VRC) Phase IV whitepaper. As promised: this one does a true deep dive on Application Virtualization in VDI. We think we have interesting new content, and more importantly, many new insights. The primary goal of Project Virtual Reality Check phase IV is to investigate the overall scalability impact of Application Virtualization solutions within VDI. The three biggest and most commonly used vendors in the VDI market space are investigated: Citrix Application Streaming, Microsoft App-V and VMware ThinApp. These three solutions were compared in different streaming configurations.
It is currently almost impossible to conceive a VDI deployment without Application Virtualization. The management benefits of Application Virtualization are real and proven, especially within centrally hosted virtualized desktops. By isolating/virtualizing applications and streaming these on demand, a much more dynamic and flexible delivery of applications is possible in comparison to classic MSI installations. Typically, when a VDI deployment needs to support many applications, Application Virtualization becomes a key component to its long term success. Besides all the Application Virtualization benefits there are some down-sides as well. Some of these are: not all applications can be virtualized, interaction between applications can be a challenge and there is an overhead on the system resources such as CPU, Memory, storage.
Depending on the use case scenario, Project VRC discovered that this impact can be significant. Test results show that Application Virtualization has impact on the VDI user density, which can be decreased by 20% to 45% when Office 2007 is completely virtualized. This should be considered as a worst case scenario. When only a couple of specific (business) applications is virtualized, the session density decreases by only 3 to 12%. In practice the Application Virtualization overhead will be highly dependent on how often virtualized applications are started, and how much file IO and registry access they generate: specifically the creation of the virtualization ‘bubble’/environment for the application can have a significant overhead.
Both Microsoft App-V and VMware ThinApp are very close in overall performance overhead, resulting in very similar VSImax scores. However, Citrix Application Streaming overhead was considerably higher: the overhead is currently more than App-V and ThinApp. The highest VSImax score was achieved with ThinApp 4.6, where the ThinApp packages were locally stored in the VM image. From a disk I/O perspective VMware ThinApp showed the least overhead throughout the test. Interestingly, the response time of the file-open dialogue is much higher with Citrix Streaming, this clearly impacts VSImax results. Also, it is interesting to see how Application Virtualization is maturing, for instance ThinApp 4.6 clearly outperforms ThinApp 4.5 in our tests. The storage impact on read and write IO was also investigated and the general conclusion is that streaming applications will decrease the read IOs by 20% to 44% and increase the write IOs by 20% to 44%. From a management point of view, choosing for demand application streaming as the delivery method brings considerable management benefits and will offload read I/O’s. However, the impact on write I/O’s should not be neglected.
If you are looking for an independent advise and a ‘Reality Check’ in relation to virtualizing Terminal Server and Desktop (VDI) workloads, if you are curious about the impact of different hypervisors and the performance differences with various hardware, if you are searching for best practices for your virtual Desktops and if you are curious about the performance impact of different Application Virtualization solutions within VDI … the different Project VRC whitepapers are a must read. The ProjectVRC phase IV whitepaper "Application Virtualization Impact on VDI"is available for download here