The Pervasive Data Center

Although VMware got its start with a desktop virtualization product aimed at developers, the company today is best known for bringing server virtualization to the mainstream.

Creating multiple virtual servers on a single physical system lets IT departments consolidate applications onto fewer computers and thereby cut costs. Over time, server virtualization has also enabled a variety of products and approaches that can simplify IT operations and generally make data centers more flexible.

VMware has continued to invest in virtualization aimed at the client. This includes client-side hypervisors such as its original VMware Workstation product. However, products and technologies associated with delivering applications and user desktops to the client are really the main focus.

Application and desktop delivery sometimes makes use of client hypervisors but it's a largely separate category of technology that's fundamentally about centrally managing user applications and/or operating-system images. In VMware's case, virtualized desktops fall under the VMware View name.

On Monday, VMware announced VMware View 4, the latest version of its virtual desktop portfolio.

Much of VMware's development focus with View 4 was in the area of the user experience--that is, making applications and desktops delivered from a central location perform with the same responsiveness and fidelity as if they were installed on a local PC, in the usual way.

Historically, this user experience has been one of the stumbling blocks for desktop virtualization in general. Older forms of Citrix Presentation Server (now rebadged and modernized under the XenApp label) and initial virtual desktop infrastructure (VDI) implementations very much tried to simplify management and otherwise deliver direct benefits for IT operations. Whether users liked using the products was secondary.

As a result, desktop virtualization has been mostly something used by what are often called "task workers." Think call centers and other groups of users with specific jobs to do and not much say about the tools they use to do it. In general, desktop virtualization promoters have focused too much on delivering benefits to IT and not enough on delivering benefits to users. (They've also arguably paid too little attention to keeping up-front costs down and relied too much on promises of soft cost savings down the road.)

One of the technology pieces that VMware is leaning on to improve user experience is the PC over Internet Protocol (PCoIP). PCoIP was originally developed by Teradici to improve the responsiveness and display quality of virtual desktops. However, in Teradici's initial implementation, specialized hardware was needed on both ends of the wire. This effectively made it a premium solution for situations in which cost wasn't a factor, such as for financial traders and government agencies for which security considerations are paramount.

VMware has worked with Teradici to create a software-only version of the protocol. Desktop virtualization Chief Technology Officer Scott Davis goes into a lot of the details on his blog.

It's a User Datagram Protocol-based server-side protocol that transmits compressed bitmaps or frames to the remote client. This has the advantage of being able to make real-time adjustments to account for the available bandwidth and latency of the communications channel; the display quality degrades, if there isn't enough bandwidth but things still "work."

Although details differ, there are similarities to Sun's Appliance Link Protocol--which is well-regarded for its ability to deal with poor-quality connections. (A downside of server-side protocols is that they consume processing horsepower on the server, where it tends to be more expensive, rather than on the client.)

VMware will continue to support other remote display protocols, most notably Microsoft's Remote Desktop Protocol. However, VMware is clearly positioning PCoIP as its favored technology and a point of competitive differentiation for VMware View in general.

Also in the graphics area, View 4 adds "multimonitor, adaptive display support--resolution optimization for each monitor, with an option to pivot and rotate the display output, supporting rich audio and video content with increased performance."

Other user experience enhancements generally relate to better integration with the overall desktop environment. For example, View Printing automatically discovers local printers without the need to install print drivers. View Limited Access provides a single point of authentication across VMware View environments, Windows Terminal Servers, Blade PCs, and remote physical PCs.

VMware View 4 comes in two editions. The Enterprise Edition includes the basics: VSphere 4 (the back-end server virtualization product), VCenter 4 (management), and View Manager 4 (for provisioning user access). It's priced at $150 per concurrent connection.

The $250-per-concurrent-user Premier Edition adds ThinApp 4 (for delivering ad hoc applications that aren't part of a master image) and View Composer (for managing images), both capabilities that would typically be desired in a large or sophisticated deployment.

VMware as a whole approaches the world from the perspective of the enterprise data center. Delivering desktops from that data center was somewhat of a sideshow. Is it now as focused on application delivery as, say, Citrix? Not really. But that said, desktop virtualization has moved beyond the sideshow stage at VMware.

VMworld, which took place last week in San Francisco, was hopping.

In fact, the number of attendees appeared to overwhelm many of the conference's educational labs in the early going. And the many vendors I spoke with at the event were happy about their booth traffic and the show in general. Now that I've had a bit of time to digest and distill three days of whirlwind activity, five points stick with me:

1. We're seeing virtualization--as technology, products, and solution sets--start to mature in many respects. Or at least the current phase of it. Fellow analyst Judith Hurwitz described how she "was left with the feeling that we are in between generations of technology at this year's VMworld."

For me, this conclusion comes out of the observation that there was relatively little on display related specifically to server virtualization that was fundamentally new and different. That's not to suggest a lack of vendor activity. Anything but. However, the activity largely took the form of new iterations and building out on existing templates.

2. Legitimate cloud computing was much in evidence. But, my, the cloud washing was fierce. Many, many companies offering management and other products relating to virtualized infrastructure were eager to present themselves as playing in the nebulously defined "private cloud" space.

VMware itself was as guilty as anyone. With the latest version of its virtual infrastructure product, now dubbed vSphere, already launched back in April, VMware's focus at the show tilted heavily toward cloud computing.

While there were a few specifics, such as vCloud Express, much of this took the form of forward-looking generalities. For example, VMware gave a lot of airtime to the notion of hybrid clouds that bridge private and public networks even though this is largely an architectural theory at this point.

3. So was anything both new and real? Yes. A couple things. One was I/O virtualization, which can be thought of conceptually as separating computing from I/O (network and storage connections mostly) and allowing that I/O to be shared and dynamically allocated. It's not really a new concept. Like many things, it has its roots in the mainframe and has, more recently, found a home in blade designs from the likes of Cisco Systems, Hewlett-Packard, and IBM.

However, the current crop of products are intended to work with standard rackmount or blade servers. Xsigo uses InfiniBand-based technology. Virtensys, Aprius, and NextIO essentially just bring PCI Express out of the server. This is a relatively young technology area but one worth watching.

4. Client-side virtualization was also a hot area even with Citrix and Microsoft--in many respects the top dogs in this space--in semi-exile from the show.

It's an exciting and evolving landscape with many new approaches and products. This includes work on protocols to improve the user experience over network connections of different types; Wyse, once exclusively a thin client purveyor, is now heavily focused here. We're also seeing a general trend toward making more effective use of the processor and graphics resources on the client rather than making the server and network do all the work; Wanova is a start-up that made an announcement shortly before the show in this area.

5. My last takeaway is a sort of meta point. The way that we do computing is changing in rather significant ways and virtualization--together with its related but distinct cousin, cloud computing--is at the focus of that change.

This is fundamentally a change in how we operate computer systems rather than, say, how we write software for them. However, because it ultimately affects how applications get delivered and computing is accessed, it has far broader implications than for just data center operators.

VMware's financial results from the second quarter of 2009 are out. They beat revenue and income estimates but those estimates were far less euphoric than during VMware's spectacular growth days of a few years back. Second-quarter revenue was $456 million, flat from the second quarter of 2008. Operating income on a GAAP basis was down 38 percent from the year-ago quarter and down 14 percent non-GAAP.

International revenue saw about 3 percent growth but this was counterbalanced by a similar decline in the U.S. International revenue is now almost equal to those in the U.S.--$222 million compared to $234 million.

One notable facet of the earnings release is that the shift to services revenue--including both software maintenance and professional services--continued at a rather rapid pace. The company is best-known for its virtualization products that relate to server infrastructure. Services revenue was up 32 percent from the year-ago quarter while licenses were down for the same period. We saw a similar trend last quarter as well.

In fact, VMware's services revenue now equals the revenue that it gets from software licenses. To some degree this reflects more software maintenance dollars coming from a bigger installed base. However, in general, software companies like to see revenue coming disproportionately from licenses because the cost of selling an additional license is relatively small.

VMware's financial statements back this up. The cost of license revenue was about $23 million last quarter; the cost of services revenue was $54 million. A heavy shift toward services is not where VMware wants to go long term.

LAS VEGAS--The Day One keynotes at Citrix Synergy 2009 were about users and desktops. Today was nominally about data centers and clouds--of which there were a variety of announcements. However, Citrix's XenClient ("Project Independence") loomed large as well.

Of the products discussed on stage, XenClient is perhaps furthest from being a fully realized product. But is also offers an intriguing window into how the PC as we know it is likely to fundamentally change over the coming years.

XenClient is a "Type 1" native hypervisor that sits on a PC and hosts one or more guest operating systems. This approach contrasts with the "Type 2" hosted hypervisors that are far more common on PCs today.

There are good reasons why we tend to see native hypervisors on servers and hosted hypervisors on desktops. Native hypervisors are higher performance, especially when it comes to interacting with networks and disks. As a result, it wasn't until native hypervisors like VMware ESX Server and Xen came to market that x86 virtualization started to seriously move beyond useful but relatively narrow uses such as in test and development labs.

The downside of native hypervisors is that, because they sit directly on top of a system's hardware, they have to take over a variety of the functions that an operating system usually performs. For example, a native hypervisor has to deal with things like power management and needs to know how to talk to graphics cards and chips, network and storage adapters, and other system hardware.

(Depending upon the virtualization architecture in question, some device interactions can be passed through to the guest operating systems, but the point remains that a native hypervisor is exposed to hardware details and idiosyncrasies that are masked if the hypervisor is hosted on an operating system.)

The great diversity of client hardware relative to server hardware therefore makes running native hypervisors on a PC tricky business.

It's also been the case that vendors haven't exactly pushed client-side virtualization--in contrast to using application virtualization to deliver software to clients--in a broad way. Hosted virtualization products handle specific use cases such as security (VMware ACE), running Windows applications on Macs (Parallels Desktop for Mac, VMware Fusion), and software development (VirtualBox, VMware Workstation). Start-ups are also tackling the security angle with alternative approaches. RingCube uses containers. Neocleus uses a Xen-based native hypervisor.

But no large vendor has seriously pushed a broad-based Type 1 hypervisor for the client. Microsoft, for its part, has been publicly skeptical about the idea. (Not especially surprising given that Microsoft has only reluctantly embraced virtualization--in part because native virtualization takes over some of the traditional tasks of the operating system.)

That changes with XenClient, a project that Citrix has collaborated on closely with Intel.

Here's how Citrix describes XenClient and its vision for desktop computing:

XenClient is a strategic product initiative with partners like Intel, focused on local virtual desktops. We are working together to deliver on our combined vision for the future of desktop computing.

This new virtualization solution will extend the benefits of hosted desktop virtualization to millions of mobile workers with the introduction of a new client-side bare metal hypervisor that runs directly on each end user's laptop or PC. This together with an innovative back-end desktop management solution for creating, delivering, and updating corporate desktop computing environments will transform the way corporate desktops are delivered and managed, giving IT all the security, simplicity and cost savings of centralized management, with an unprecedented level of performance, personalization and freedom for end users.

To net it out, Citrix is pushing for a future in which a hypervisor is a standard abstraction layer for every cleint and server--just the way that x86 architectures of all stripes are architected and built. Think of it as a BIOS on steroids if you will.

Citrix's interest here is obvious. After all, its strategy is to make money from managing virtualized environments. Thus, continuing with a theme from Synergy's first day, XenClient--like XenServer--will be free when made available later this year.

Intel's interest here is that XenClient is specifically targeted for systems with vPro technology. vPro includes:

• Intel Virtualization Technology (VT)--hardware assists for improved virtualization performance
• Intel Trusted Execution Technology (TXT)--formerly called LaGrande, provides hardware-based rooted security
• Intel Active Management Technology (AMT)--hardware management technology

Intel's Pat Gelsinger said in his keynote that vPro is ramping quickly--he claimed it was in 60 percent of the Fortune 100--but Intel is doubtless actively seeking more reasons to get businesses to upgrade to their latest and greatest client platforms.

The vision here seems a sound one. After all, IT vendors have essentially been adding layers of abstraction to mask complexity since the beginning. Even an operating system is an example of abstraction (actually many of them rolled into one software package). And use cases involving personal PCs used to access corporate networks or protected VMs that run security scanners seem far less esoteric than they did even just a couple of years back.

The question is more one of time frame. When do compelling uses get made available by software vendors in largely transparent ways for end users who are not developers or otherwise ready, willing, and able to explicitly manipulate multiple virtual machines on a single client? It isn't this year but there's a lot of reason to believe that this is the direction the client is headed.

VMware's first-quarter financial results are out.

Revenue increased 7 percent from the first quarter of 2008 to $470 million. GAAP net income for the first quarter was $69.9 million, or 18 cents per diluted share, compared to $43.1 million, or 11 cents per diluted share, for the first quarter of 2008.

These are respectable results, though "analysts, on average, were expecting a profit of 20 cents per share on sales of $474.4 million, according to a poll by Thomson Reuters." Furthermore, guidance was disappointing, Reuters noted:

VMware, majority-owned by EMC, estimated second-quarter revenue to be flat or down from $456 million in the year-ago period. That was below analysts' average forecast for revenue of $501 million, according to Reuters Estimates.

Difficult economic climate or not, this is still a sharp change from VMware's growth rates of a few years back (though to be sure, it's a much larger company now, making it hard to maintain that sort of rate). And some financial analysts are getting grumpy, Reuters reports:

"It's a serious miss. It is not just the magnitude that is troubling. It is the reason they are giving," said Global Equities Research analyst Trip Chowdhry. "There is something fundamentally wrong--either in product strategy or sales execution."

This seems overstated, from my perspective, as a watcher of virtualization, as well as related technologies and companies. VMware, it seems to me, has done a great job--first under founder Diane Greene and now under Paul Maritz--in keeping VMware solidly in front of the virtualization wave and adding value on top of base components that have commoditized to a certain degree. And it's just rolled out an impressive new set of products, vSphere 4--its new Virtual Infrastructure suite.

(Commoditization isn't really the right word for what has happened to the hypervisors that form much of the foundation for server virtualization; however, it's certainly become hard to charge much money for them.)

That said, and top-line and bottom-line results aside, there were some underlying details that caught my eye. That's these, according to VMware's release:

First-quarter services revenues were $213.3 million, a 48 percent increase from last year. VMware's business mix continues to shift, with services revenues becoming a larger proportion of total revenues.

In the first quarter, services revenues were 45 percent of total revenues, compared to 33 percent a year ago. Driven by the challenging macroeconomic environment, license revenues were $257.0 million, a decline of 13 percent from a year ago.

That's a striking shift toward services from product. Contrast this to another large independent software vendor, Oracle, which garnered only 22 percent of its revenue from services in its last fiscal quarter--a figure that is actually slightly down from the year-ago period. In my experience, Oracle's mix is fairly typical of product companies.

This bothers me a bit for a couple of reasons. First, services require a lot of dedicated headcount. They also don't scale especially well--you're essentially renting out people. Contrast this to products; once you cut the CD, you can make as many copies as you want. (Obviously, there are limits to sales channels and so forth, but software licenses are much more scalable.)

The other is that it points to one of the impediments to virtualization growth; it's relatively complex--at least once you get past the consolidate-one-or-two-servers phase. To be sure, some of that services revenue is education (about 10 percent), which is reasonable enough in a technology area that's still young. But a full 80 percent is consulting--which says to me that this virtualization stuff isn't as easy as it should be.

I noted last month that embedding the code for server virtualization directly into the hardware, something called an embedded hypervisor, hasn't taken off to any significant degree.

Rather, most IT shops continue to purchase virtualization as a third-party add-on (typically from VMware or Citrix), or they acquire it as part of Linux distribution or Microsoft Windows.

Many of the management and other services associated with virtualization are going to be added on, in any case. However, the thinking of a lot of people went, wouldn't it make sense to at least get the foundation in place as part of the server purchase, given that we're seeing more and more interoperability between the various hypervisors and the software that exploits them?

Since writing that piece, I've received a variety of interesting comments, and had some discussions with IT vendors and others I thought worth sharing.

Reader rcadona 2k commented:

Adopting a hypervisor is an active choice or, in most cases, a surrender of your hardware. Embedded hypervisors aren't just a BIOS; they require formatting your storage a particular way (VMware VMFS, Hyper-V NTFS, LVM/raw LUNs for Xen). The virtual BIOS features amongst hypervisors for the guests are not standardized, and the virtualized guest devices are not standardized. When you pick a Type-1 hypervisor, you lock yourself into another "platform."

Some good points here. We have a a bad habit in the IT industry of using the word "commodity" when we really mean things along the lines of "widely used with variants available from multiple sources" (and, therefore, relatively low-price). Hypervisors are an example of this. They all do roughly the same thing. There are a variety of suppliers. And the price for base-level hypervisors has been sliding toward zero.

But they're not commodities. For all the interoperability work that has been taking place at the management and services layer, there remain significant product differences that affect things as substantial as an IT shop's storage architecture. Some of these will go away--or at least be abstracted away--over time, but not all necessarily will.

Given that the choice of hypervisor still matters in such important ways, it's understandable that people continue to buy them primarily as an explicit component of the broader virtualization software ecosystem that depends on them.

Another feedback theme was just that we're still in the early days of virtualization. Perhaps most notably, when VMware rearchitected ESX Server to create the embedded ESXi version, not all the capabilities and features carried over. (Without going into all the details, the full ESX uses a Linux-based service console to manage the hypervisor; ESXi does away with this and is much thinner as a result. However, the current iteration of ESXi doesn't fully replicate all the capabilities provided by that console.)

However, the VMware partners that I've spoken with fully expect that upcoming ESXi versions will soon reach parity with the older ESX architecture and that this will therefore cease to be a reason to shy away from the embedded approach.

I remain skeptical that embedded, just-built-in hypervisors are going to become the norm that it once seemed they would be. If nothing else, Microsoft's Hyper-V--most likely predominantly installed as part of Windows--will tend to hold sway in Microsoft-centric environments, of which there are many.

At the same time, it's too early to write off the idea of embedding hypervisors just because the idea hasn't gained a lot of initial momentum.

Here's the basic question: where does the hypervisor--the software layer that underpins server virtualization--live and who owns it? Is it just part of the server or is it just part of the operating system?

For now, to be sure, it's often something that IT shops purchase from a third-party--we're mostly talking from VMware here. However, pretty much everyone expects that over time this foundational component will be increasingly built-in--even if the higher-level value-add management and virtualization services that make use of it are explicitly purchased from a variety of sources.

Virtualization vendors have often considered this an important question.

A few years back, I had written a piece about how Novell and Red Hat were adding the Xen hypervisor to their Linux distributions. And that Microsoft had made clear its intention to add virtualization to Windows--technology now known as Hyper-V. In short, virtualization was starting to move into the operating systems of a number of vendors.

Well, that notion didn't sit well with Diane Greene--then CEO of VMware--as she made clear to me by coming over and grabbing me by the lapels(only somewhat figuratively) at an Intel Developers Forum event. From Diane's, admittedly biased, perspective the hypervisor should be independent of any single operating system. I hadn't said otherwise. But I apparently didn't make the opposing case enthusiastically enough.

At the time, VMware ESX Server (its native hypervisor) had to be installed as with any other third-party software product. However, over time, VMware and other virtualization vendors came out with versions of their products that could be installed from a USB memory stick or other form of flash memory. It was called ESXi in VMware's case.

Thus the embedded, or at least embeddable, hypervisor was born with rumors throughout 2007 becoming product announcements in September of that year.

There's actually a lot to be said for the embedded hypervisor. Lots of IT environments--especially enterprise ones--do indeed have a mix of operating systems and operating system versions. Given that, there is indeed a lot to be said for the idea that hypervisors just come with the server as a sort of superset to the firmaware, like BIOS, already loaded on every system. Then IT administrators could just configure any guest OSs they want on top.

It's logical. But it's not really playing out that way--at least so far.

After all the initial excitement in late 2007, embedded hypervisors didn't really go anywhere in 2008. Instead, Microsoft's Hyper-V rolled out and KVM found its way into the main Linux kernel as an alternative style of Linux virtualization backed by Red Hat.

Whether or not it makes "sense," in some theoretical, architectural sense, it's no longer clear to me that embedded hypervisors are going to be the path that the industry predominantly follows.

Rather, at the moment, homogeneous environments are tending towards whatever is built into the OS. And enterprises are going to their ISV of choice--sometimes Citrix for XenServer--but far more often VMware for ESX.

At the very least, it now looks as if--for the foreseeable future--IT shops will acquire virtualization, including hypervisors, in a variety of ways that vary as a function of their individual requirements, circumstances, and vendor alignments.

Analyst Brian Madden identifies desktop virtualization as a major 2008 virtualization theme:

If you could sum up the year with a single theme, that theme would be "desktop virtualization is here to stay." I don't want to go so far as to say that desktop virtualization is mainstream, but 2008 saw Microsoft, VMware, and Symantec getting serious about it, and Citrix fighting to keep the lead (it'd) established via XenApp over the past decade.

I concur.

"Desktop virtualization" isn't a single thing; it's really a shorthand for a variety of approaches, the common thread of which is that they're not traditional Wintel "fat clients." And it dovetails with other technology approaches--such as rich Internet applications (RIA) and browser-based application access--that are only virtualization in the most conceptual sense.

I started seeing a swelling interest in alternative ways of delivering applications and software services to a variety of clients in 2007. But I agree with Madden that the trend accelerated in 2008, albeit at a measured pace often driven by security and compliance concerns more than return-on-investment arguments.

2008 saw Citrix rationalize its entire virtualization portfolio around the Xen nomenclature--breaking from its successful but narrow Presentation Server roots. And VMware's View announcement in December filled out a client-side portfolio that had been missing some major pieces previously.

Microsoft, meanwhile, rolled out Hyper-V and announced a new version of its application virtualization product. And systems vendors such as Dell, Hewlett-Packard, IBM, NEC, and Sun Microsystems also expanded or updated their offerings on the desktop side.

The desktop, as we've come to know it, has hardly gone away. New devices that depend on applications running in the network and data stored there tend to supplement, rather than replace, more traditional clients.

But some of our applications now usually reside in the network; we tend to regard an unconnected PC as a crippled thing. And that opens up a frame of mind that will move more and more "state" (whether applications, personal data, or other services) off local devices and into either corporate data centers or the cloud.

When I put together an overview of VMware's virtualization portfolio in May of this year, my focus--like the company's--was on their products that establish a virtualized infrastructure, and then manage and automate virtual-machine life cycles on top of that infrastructure.

It's not that VMware didn't have desktop products. In fact, its first product, still popular among developers, was VMware Workstation. And in practice, it has the default back-end server virtualization used for virtual desktop infrastructure installations. I went on to write that:

For many companies, this desktop portfolio would be an enviable product lineup in its own right. However, it's not at the core of VMware's strategy. VMware's primary focus is, rather, on back-end infrastructures, not the client.

This reflects, in part, where the most interesting use cases lie and, not incidentally, where there's the most money to be made. It's also a function of where computing is headed--into the data center and into the cloud.

VMware was clearly doing work behind the scenes to amp up its presence in virtualization related to clients. However, it remained a work in progress and largely out of the limelight--more a set of point products and solutions than a systematic capability.

That's now largely changed. With its VMware View announcement on December 2, the company now has both a fairly complete set of client-side virtualization products and a more structured approach to organizing the portfolio.

Before getting into what VMware View is, it's worth noting what it is not. It's not an umbrella for all VMware work related to clients. Thus, products such as VMware Workstation, VMware Fusion (desktop virtualization for the Mac), and VMware ACE (which extends corporate resources to unmanaged PCs) remain an independent set of products for now.

That said, an experimental "offline desktop" capability that VMware announced as part of View dovetails with virtualization on the desktop (using a new client hypervisor project still under development), so it wouldn't surprise me to see further integration over time.

Rather, View is focused on delivering virtual desktops (and applications) hosted on back-end virtual infrastructure to client devices. VMware describes View as a renaming of Virtual Desktop Infrastructure (VDI), though it also rolls in both other existing products and new ones. In addition to the aforementioned "offline desktop," View covers three primary areas:

VDI: This is a combination of VMware Infrastructure--that is, the software services running in the data center to create and manage the virtual machines that are being delivered to the desktop--and View Manager. Manager is the renamed Virtual Desktop Manager, the "connection broker" tool that handles tasks such as connecting the right client to the right virtual machine.

Application virtualization: ThinApp is the result of VMware's acquisition of Thinstall in January 2008. It can be thought of as a complement to VDI. Whereas VDI delivers a complete operating-system image (along with all its applications) to a client device, application virtualization delivers a specific application to a client, whether virtual or physical.

Storage optimization: View Composer is a new product that uses "Linked Clone" technology to create virtual desktops and propagate updates from a single master. One of the reasons that this type of software is important in VDI installations is that typical desktop images contain many of the same files. VMware estimates that Composer will typically reduce storage requirements by about 70 percent.

Overall, VMware remains more server-centric than client-centric. In a sense, it's a mirror image of Citrix in this regard, reflecting differences of historical focus. Prior to acquiring XenSource, Citrix was solely about delivering applications to clients (as was its close partner, Microsoft).

VMware, on the other hand, really made it big by enabling companies to consolidate servers and thereby reduce the number of physical boxes they had to buy. However, there's an ever-increasing interest within IT shops in moving away from traditional approaches to deploying and managing desktops. So, if you're a serious virtualization player--and VMware's the biggest such--you pretty much have to make a serious client play.

And VMware is doing so.