Citrix and VMware face-off over client hypervisors

Last month at VMworld, VMware took a major step forward in its desktop virtualization vision with the introduction of View 4.5.  On hand for the launch was Gartner Research Vice President Chris Wolf who confirmed that View 4.5’s improved scalability coupled with the addition of role-based delegated administration change auditing features and the ability to support Windows 7 meant that View 4.5 joined Citrix XenDesktop 4.0 in fulfilling Gartner’s requirements for an enterprise-class server hosted virtual desktop platform. Although, View 4.5 is more notable for a feature that is not required to obtain Gartner’s blessing.

View 4.5 and XenDesktop 4.0 both fulfill Gartner’s criteria for enterprise class server hosted virtual desktop platforms, this does not mean that XenDesktop 4.0 and View 4.5 are directly comparable, either in terms of their available feature sets or the overall maturity of the products.  Certainly Citrix were later to market with XenDesktop that VMware were with View (formerly VMware VDI). However, XenDesktop is a more mature product than View, due in large part to Citrix’s ability to leverage both its experience in developing XenApp, as well its ability to re-use many of the associated technologies as components of the XenDesktop suite. As a result XenDesktop has significant advantages over View, especially in more complex and more technically demanding environments such as those requiring the ability to deliver satisfactory performance on high-latency, low-bandwidth wide area network connections.

There’s no question that the addition of these features is critical to View 4.5’s market presence, however in some respects View 4.5 is more notable for a feature that is not required to obtain Gartner’s blessing as an enterprise class product – specifically the inclusion of Local Mode.  Local Mode was previously offered in View 4.0 as an unsupported “experimental” feature where it had the somewhat awkward label “Off-Line Mode”).  Local Mode extends View from being a server hosted virtual desktop platform to a universal virtual desktop platform, capable of running a virtual desktop in the data center or on the desktop.

VMware introduced view 4.5 at VMworld as being the first shipping product with this capability.  While it is absolutely correct that View Local Mode shipped before the formal release date of its primary competitor Citrix XenClient, View was not the first shipping desktop virtualization to offer this capability.  The distinction of being the first solution to offer a universal virtual desktop hosting solution belongs with Virtual Bridges VERDE. In addition Virtual Bridges, Quest Software and Virtual Computer, both established desktop virtualization ecosystem vendors, have announced a technology alliance that will bring together Quest vWorkspace and Virtual Computer NxTop to provide their own universal hosted virtual desktop solution in the near future. (The Virtualization Practice’s Andrew Wood provided coverage of the Quest Virtual Computer alliance here). Virtual Bridges is still very much a niche player in the market, and the Quest, Virtual Computer alliance while very promising has yet to deliver anything . Which means that  in the short term at least most enterprises will focus their attention between Citrix and VMware.

Regardless of any minor inaccuracies in VMware’s announcement, the availability of Local Mode was a major step forwards for the industry. The ability to host a desktop workload on the most appropriate platform for the work being performed is a major step forwards.  By reducing the dependency on the data center to host the desktop, the cost disadvantage of server hosted virtual desktop platforms can be diminished which should have the effect of accelerating adoption to at least a small degree.  This move should also help desktop virtualization vendors such as Wanova and Moka Five who already look to the endpoint as being the ideal hosting platform and do not require the massive virtual infrastructure in the data center that View requires.

Moving on to the present and the launch  of XenClient as an integral part of XenDesktop 4.0 Feature Pack two (XenDesktop 4.0 Feature Pack two will be covered in-depth in a future briefing) any opportunity for VMware to obtain advantage over being first to market is fast dissipating. However; even with the availability of XenClient, VMware still has an opportunity to establish a significant differentiator between View and XenDesktop.  Just as it is not possible to make a wholly satisfactory comparison between XenDesktop and View; XenClient and View Local Mode are sufficiently dissimilar to make any direct comparison difficult here as well.

The primary technical differentiator here being the type of hypervisor used, XenClient is a type I, or bare-metal, hypervisor; whereas View Local Mode uses a type II hypervisor.  From an architectural perspective, a type I hypervisor has significant advantages over a type II hypervisor, offering improved security, greater performance, as well as having being able to take advantage of dedicated virtual appliances to perform management and support functions  without imposing on the guest virtual machine.  However, from the standpoint of implementation, the advantage lies with VMware. Just as Citrix was able to build on its experience in developing XenApp to create a mature desktop virtualization solution, so VMware was able to build on its experience with previous type II desktop hypervisors to develop View Local Mode.  Technical differentiation aside, the other major factor in determining the relative market success of Citrix and VMware will be the point at which IT organizations decide to move to widespread adoption of client hypervisor technologies.  If there is widespread adoption in the next nine to 18 months, XenClient with its limited hardware compatibility list (HCL) and dependency on Intel vPro processors will be at a distinct disadvantage.  In the longer term however, the advantage that View Local Mode possesses will diminish as Citrix works to increase the length of XenClient’s HCL, at the same time as vPro processors roll out across the majority of corporate desktops that barrier to adoption will also dissipate.  In the event that client hypervisor adoption reaches critical mass before XenClient is ready for widespread deployment, it is possible that Citrix could consider adopting its own type II client hypervisor.  Several options exist here; partnership with the open-source Xen community which has been working on its own type II client hypervisor for some time now , especially given that Citrix provides such a large input to open-source Xen; Alternatively, Citrix could increase its stake in Virtual Computer and offer it as in interim solution.  Conversely if enterprises are slow to adopt client hypervisor technology, VMware may choose to return to its own type I client hypervisor development program. Either way, given the level of uncertainty, it is too early to make any meaningful predictions regarding future market share.

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