Parallels Virtuozzo Containers vs. VMware Virtual Infrastructure:

Parallels Virtuozzo Containers vs. VMware Virtual Infrastructure: An Independent Architecture Comparison

TABLE OF CONTENTS Introduction...3 A Tale of Two Virtualization Solutions...5 Part I: Density...5 Part II: Efficiency...6 Part III: Scalability...6 Part IV: Manageability...7 Different Computing Environments Require Different Virtualization Solutions...7 2

ith so much hype and buzz in the market surrounding the idea of virtualization, it s easy to get caught up in the excitement. For the uninitiated, the differences between Hardware Virtualization tools like VMware Virtual Infrastructure and those that drive O/S Virtualization like Parallels Virtuozzo Containers are of little consequence. But in reality their goals and feature sets are vastly different. With all the types of virtualization products in the market today, understanding their nuances and ultimately finding those that work best in your environment can be challenging. Specific to the products that drive Hardware Virtualization and O/S Virtualization, these two architectures are designed with different workloads and environments in mind. Some environments, like those with high density or high levels of O/S homogeneity, may work better with one product than with another. Other environments, where widespread O/S support is a high priority, may work better with another. Finding the correct virtualization tool to solve an organization s consolidation needs depends on the needs of the environment combined with the feature sets of the product. This white paper will attempt to demystify some of the complexity in that decision-making process. Focusing on a technical and market-based comparison between the VMware Virtual Infrastructure platform and the Parallels Virtuozzo Containers toolset, this independent comparison will attempt to shed some light on the differences between these two types of virtualization. This white paper will discuss the specifics of these two architectures as well as the associated market pressures that tend to drive organizations towards one solution versus another. Our first candidate architecture, Hardware Virtualization, is the virtualization concept being mastered by VMware through its VMware Virtual Infrastructure platform. This architecture solves many problems associated with consolidating computers in a heterogeneous environment. Our other architecture, O/S Virtualization, is a much different concept being perfected by Parallels Virtuozzo product. It provides ultra-high density and resource efficiency for many computing environments. You ll find that in some cases VMware Virtual Infrastructure works best. In others, Virtuozzo Containers can be a better solution for your environment. Let s start by looking at a few of the realities surrounding virtualization in the IT marketplace today: Gone are the days of asking, So, what is virtualization? Those questions today give way to, How best do I fit it into my environment? During virtualization s early years, articles and white papers discussing the basics of the technology were numerous and plentiful. Those articles created much of the common knowledge we know today surrounding virtualization solutions. One focus in those early documents, however, was their focus on Hardware Virtualization as the singular virtualization architecture. Enlightening the world s IT people in the early days involved much education involving the use of Hardware Virtualization tools for consolidating servers and workstations into containers virtualization environments. Some of the confusion with today s expanded solution set lies with a historical bias associated with those early attempts at educating the public. With newer options that leverage different architectures, the early understanding of the public as to what virtualization is needs a bit of a refresher. The earliest products and solutions for virtualization have been augmented with newer architectures such as O/S Virtualization, Paravirtualization, and others that can fulfill some needs in better ways than the traditional Hardware Virtualization architecture we ve known about for many years. 3

One of the most critical components in any virtualization assessment is an understanding of all the potential architectures as well as how they can fit into the computing environment. When it comes to virtualization products and solutions, it s all about the layer. As they say in real estate, it s all about location. With virtualization, it s all about the layer. Referring to virtualization and the products that support and drive virtualization that layer refers to the level within the system at which the virtualization occurs. Hypervisor-based Hardware Virtualization solutions include their layer of processing either atop an existing operating system or in the case of VMware Virtual Infrastructure directly on top of the hardware bare metal. Doing virtualization in this way bestows some benefits to the environment. Laying its hypervisor very close in proximity to the physical hardware, VMware s solution can robustly support multiple operating system types on a single physical host. Those individual virtual machines are fully independent from each other and none rely on any other for their composition or processing. Due to their emulated onboard device drivers, they re also highly portable between different hosts running on different platforms. This complete isolation and independence between individual virtual machines is at once VMware s greatest strength and greatest area of management complexity. As virtual machines are effectively segregated units, their management must be done in ways very similar to segregated physical machines. Patching, software management, resource allocation, and security are all horizontally scaled as the number of virtual machines increases. This can lead to a virtual sprawl of devices to manage as the environment scales. In effect, by virtualizing your environment in this manner, you require the same level of management effort as with physical machines because each virtual machine is managed individually. Compare this scenario to what is experienced in environments that leverage O/S Virtualization, like what occurs with Virtuozzo Containers. Within these virtualization environments, or containers, the layer operates atop an existing full operating system like Microsoft Windows or Red Hat Linux. Virtuozzo does not make use of a streamlined O/S or a hypervisor layer. Instead it uses the virtualization layer as a mechanism for extending the resources of a single operating system to multiple, isolated, additional systems that all reside on the same host. Virtuozzo s virtualization layer provides for the creation of segregated Containers. Although a fully-independent computer, an individual Container is often made up of much of the same files that make up its hosting O/S through Virtuozzo s unique copy-on-write technology. Individual files, registry settings, and libraries within the Container can and are updated throughout that computer s lifespan, creating uniqueness between the onboard Container and its host. Thus, running 25 Containers atop a single host creates 25 individual machines, even though those machines share many of the same files. When the files on an individual Container changes, that file is changed for that Container only. Virtuozzo Containers additionally gains management advantage through server templating. The linkage between the host and its onboard Containers means that any update of files on the host has the ability to directly and immediately impact all residing Containers. Patching the host can immediately patch all the Containers. Adding an application to the host can immediately add that application to all the Containers. Applications destined for individual Containers rather than the host itself can be packaged prior to deployment, further making possible rapid configuration changes. This process of server templating reduces the overall management cost associated with a horizontally-scaled containers virtualization environment. Virtualization is not going away, but is instead becoming ubiquitous. According to an eweek report in March of 2007, The worldwide market for x86 virtualization solutions has been growing rapidly since 2003 when it reached $205 million, according to IDC. Last year, the number topped $800 million, and IDC projects it will reach $1.8 billion by 2010. 1 This translates to an increase of nearly a billion dollars to be spent on virtualization solutions between the release of this paper and the year 2010. Compare these numbers with another report, also completed by IDC early in 2007 that reports, more than 15 percent of new server shipments will undergo virtualization in 2010, up from 5 percent in 2005. 2 Note that these numbers are really for new servers. According to a recent InformationWeek survey, 90% of polled business technology professionals have virtualization projects either in process or planned. 65% are implementing virtualization now. 3 The coming virtualization wave is more-or-less already here. With many companies feeling the strain of powering, cooling, and managing dozens or hundreds of systems not operating 1 Source: http://www.esp.eweek.com/print_article/virtualization+space+ Opens+Up/203552.aspx 2 Source: http://www.gridtoday.com/grid/1218232.html 3 Source: http://www.scaleoutadvantage.techweb.com/news/iweek20070210_ Virtualization.jhtml;jsessionid=ZZLPWHRC3RYRKQSNDLPCKH0CJUNN2JVN 4

at full capacity, the drive towards virtualization is a drive towards more efficient use of available resources. As we ll learn in a minute, there are a number of driving forces towards this massive move to virtualization. Among them, greater server density and efficiency of available resources are critical as well as improved service scalability and overall management. Aligning with these needs, one concept you ll find again and again in server virtualization is the idea of consolidation. This term defines the number of physical machines you can collocate onto a single virtualization host, and is a major factor in realizing the overall return on your virtualization expenditure. Depending on the workload requirements you intend to run within your containers virtualization environment, you ll find that some architectures have the ability to support much greater numbers of systems and therefore a higher level of consolidation than others. Many virtualization deployments fail, often due to mismatched technology and needs. Sometimes more than one virtualization solution may be the best answer. Due again in some ways to those early attempts at defining virtualization as a specific product set, some project teams may not look at all possible virtualization toolsets that fit their needs. When the needs of a computing environment don t match with the toolsets installed, it grows difficult to fully recognize the greatest return on the virtualization investment. In fact, according to a recent study by CA, 44 percent of respondents who said they had deployed server virtualization technology were unable to declare their deployment a success. Inability to quantify ROI was a key factor in their reticence to definitively claim positive results. 4 The report goes on to discuss that 71 percent of organizations that have moved ahead with virtualization have deployed, or plan to deploy, multiple server virtualization technologies -including operating system and hardware virtualization, operating system partitioning, paravirtualization, and/or clustering. As different virtualization solutions work best with different types of workloads, selecting a single one-size-fits-all solution may not necessarily be the best fit either. Finding the correct technology that matches with the needs of the computing environment is critical to getting the best return. For example, in some situations the environment may require operating systems of different types to work together in supporting a network service (e.g. a Linux-hosted database that works with a Windows-based web server). The performance of that service may be better when its servers are collocated onto a single virtual host. This situation might work best with a Hardware Virtualization solution like VMware Virtual Infrastructure. In another example, a different environment might be very focused on a single operating system. The individual configuration of servers in this environment may be very similar to each other (e.g. a code development activity that requires multiple testing environments or a hosted desktop environment). They may require high density and the lowest possible management overhead due to their similar composition and high turnover. A situation like this might work best in an O/S container such as Virtuozzo Containers. Most important is that computing environments are all different, and there can be multiple needs within the same environment. Thus, depending on its needs and complexity, it is possible that both technologies can fulfill a role. The two technologies can complement each other well. A TALE OF TWO VIRTUALIZATION SOLUTIONS Let s take a focused look now at each of these two virtualization solutions, where they work the best, and where they may not necessarily be a best fit. Our discussion here will focus on four axes that describe each product s capabilities related to Density, Efficiency, Scalability, and Manageability. Part I: Density In the world of virtualization, one concept that is of major importance to most environments is consolidation. Consolidation refers to the number of machines that can successfully work together on a single physical host. Consolidation is a function of overall performance. Higher levels of consolidation are typically gained through faster host hardware, virtual machines that require few resources, and the type of virtualization product chosen. For a Microsoft Windows system, think of the amount of time your servers spend running the System Idle Process. When servers utilize this process, they re providing no valuable work to the environment, waiting for their next instruction to complete. Industry-wide the average percentage for System Idle Process for Microsoft Windows servers is around 92%. This means that your servers are producing valuable work only 8% of the time, while consuming expensive power and cooling at all times. For many environments, the move to virtualization is part of an effort to get more valuable work out of existing server environments. The higher their consolidation density, the more virtual servers an environment can successfully host 4 Source: http://investor.ca.com/phoenix.zhtml?c=83100&p=irolnewsarticle& ID=978418&highlight= 5

on its physical hardware. VMware Virtual Infrastructure environments support the stand-up of multiple systems per physical host. The physical host s hypervisor layer handles the proxying of physical resources to onboard virtual machines that require attention. Each system is an independent entity from the perspective of its files on disk. Because each virtual machine requires its own separate file set, multiple virtual machines will require multiple copies of virtual machine files. This total independence allows for the complete segregation of virtual machines from each other. It also means that Virtual Infrastructure-based virtual machines cannot share memory, cache, or files on disk between processes across individual virtual machines. Each process running on a virtual machine is handled by the processors on the physical host and is stored within the physical host s RAM. But the running and caching of activities on one physical machine by definition cannot be shared with other virtual machines on the system. This is good from the perspective of ensuring virtual machine isolation from each other (as is in the case of virtual machines that span security boundaries), but un-optimized from the perspective of resource sharing. Containers within a Virtuozzo environment operate much differently than virtual machines within Virtual Infrastructurebased environments. File system buffers and cache within a Virtuozzo-based environment are shared between the host and any onboard Containers. This first means that a single cache can support the needs of all Containers as well as the host, which improves resource use. Since multiple virtual machines do not require their own independent and redundant locations for physical RAM and cache, this tends to reduce the overall need for RAM as well as resource-costly swapping activities. It also means that an application installed onto the host can be used by all residing Containers if desired. Any change in configuration that occurs to the onboard Container is written to the disk using a Copy-on-Write mechanism that ensures the uniqueness of the Containers configuration. All this leads to the potential for a significantly large total density that can be provided by a Virtuozzo-based environment. Furthermore, because of the high level of resource optimization, this density ratio serves for traditionally highload workloads like email systems and databases. Part II: Efficiency Both virtualization solutions are highly efficient in their use of available physical resources. With Virtual Infrastructure, the residing operating system requires very few resources to operate, arriving as a very streamlined version of a Linux kernel. That Linux kernel s job is to facilitate the hypervisor and its proxying of physical resources to virtual machines. Due to Virtual Infrastructure s very streamlined hypervisor, its ability to support high numbers of simultaneous virtual machines is much greater as compared with other Hardware Virtualization solutions that reside atop an existing full operation system. One feature of Hardware Virtualization architectures is their reliance on emulated driver sets to support the hardware needs of the onboard virtual machines. Emulated driver sets require a translation of instructions between the driver set installed into the virtual machine and the one recognized by the host. This translation means that virtual machines installed onto one type of server will continue to function when moved to another type of server. The translation provides a layer of abstraction between the virtual machine and its physical underpinnings. A limitation of these emulated driver sets is that the process of doing the translation incurs an overhead to physical resources. Doing the translation involves additional work on the part of the host. Because the host needs to perform this work with all onboard virtual machines, it reduces the total amount of physical resources for the virtual machines. More recent computer systems with onboard virtualization extensions built into their processor chips can alleviate some of this overhead. With O/S Virtualization architecture and Virtuozzo Containers, the architecture is different. Virtualization Virtuozzo operates at a layer above the operating system rather than below it. Because all residing virtual machines are components of the host, there is no need for emulated driver sets. The driver sets of the host are the very same as the files for the onboard virtual machines. Lacking this emulated hardware eliminates the overhead of Hardware Virtualization architectures. It adds the potential of achieving performance near that of the native server itself as well as assignment of physical resources that scale to the full resources of the host server. Part III: Scalability Both Virtual Infrastructure and Virtuozzo Containers enable massive horizontal scalability for onboard virtual machines. With both architectures, their virtualization layer allows for the creation of residing virtual machines as long as available resources exist. With both products there is the need for administrators to undergo routine performance management on the server, watching for performance bottlenecks and adjusting resources or relocating virtual machines as necessary to ensure the most efficient use of available resources. Some of the mechanisms used by each product to facilitate this performance management are very similar. Both Virtuozzo and Virtual Infrastructure have the ability to adjust physical resources that are assigned to onboard virtual machines. Virtual machines can be assigned quantities of RAM, processor, network, and disk resources as necessary. 6

What is different however is in how those resources are assigned. With Virtual Infrastructure, a limitation associated with the Hardware Virtualization architecture means that only a preconfigured quantity of resources can be assigned to virtual machines. With Virtuozzo, there are no limitations. Any hardware resources available to the host can be made available to the residing virtual machines. As an example, Virtual Infrastructure has a limitation on the number of processors that can be assigned to an onboard virtual machine. Virtuozzo does not. This results in a highly optimized use of available resources, and therefore the potential for excellent efficiency in resource use. Additionally, manipulating the level of resources with Virtuozzo can be done without an impact to the virtual machine. Doing the same with Virtual Infrastructure often requires a reboot of the virtual machine. This fact enhances the ability to dynamically adjust resources as necessary to support the needs of the environment. Part IV: Manageability Lastly, no discussion regarding these two architectures is complete without the recognition of the management activities associated with their use. Virtual Infrastructure includes an excellent interface for the centralized management of all virtual machines on all physical hosts within the datacenter. This single, unified interface allows for all virtual machines to be managed from one place, no matter where they may be hosted or which operating system they run. Intrinsic to the interface are schedulable as well as scriptable interfaces for managing the virtual machines. Coding framework exposure allows for the addition of 3rd party tools for additional management as necessary. One characteristic of the Virtual Infrastructure interface is its computer-centric nature. Virtual Infrastructure and its architecture involve the running and management of virtual machines as individual computers. Virtual Infrastructure s management framework is much like the chassis of a physical machine. It provides the operating environment in which that computer can perform its function. But that chassis does not manage the internal operations of the computer. It doesn t patch, add applications, or change configurations. In environments where this is not a concern, or where other tools are already in place that fulfill these needs, this may not necessarily be a concern by administrators. Conversely, O/S Virtualization and specifically Virtuozzo Containers are a management toolset that directly manages the internal configuration of each residing Container. Due to its architecture, it is feasible to consider Virtuozzo as much as a systems management tool as a virtual machine management tool. Virtuozzo supports the creation of application packages that can be installed to any host or Container as necessary through the same management interface that handles Container administration. Containers can similarly be backed up, reconfigured, created and templatized, and have their configurations changed en masse through this same interface. In environments where the management of individual machine configurations is important and desired through the same interface as management of virtual machine configurations, these capabilities can enhance overall manageability. Above all, when using Virtuozzo Containers as the virtualization solution, there is only a single operating system to manage. Residing virtual machines with Virtuozzo, though segregated, are components of the host operating system. By not having to manage multiple operating systems, environments with Virtuozzo can focus on supporting their primary O/S without the need for the additional management and maintenance overhead associated with supporting an additional O/S. DIFFERENT COMPUTING ENVIRONMENTS REQUIRE DIFFERENT VIRTUALIZATION SOLUTIONS As has been illustrated in these pages, the needs of a computing environment will drive which virtualization solution best fits. We ve had the opportunity here to talk about two of these possible options and in what types of environments they work the best. Each product has its own strengths and weaknesses. One integrates multiple operating systems into a single platform. The other incorporates high levels of density and in-machine management as part of the platform. Both can successfully support virtual machines and operating systems of many types, including Microsoft Windows and various versions of Linux. In the end, the determination of which works best in your own computing environment is up to you. The most important facet of this determination is the understanding of how each virtualization concept functions, the features it provides, and where it can provide the best return on your virtualization investment. For more information on VMware Virtual Infrastructure, check out www.vmware.com. For more information on Virtuozzo Containers, check out www.parallels.com/learnmore. 7