All About Virtualization
- 1. VMWARE WHITE P A P E R W H I T E PAPER Virtualization Overview 1
- 2. VMWARE WHITE PAPER Table of Contents Introduction .............................................................................................................................................. 3 Virtualization in a Nutshell ................................................................................................................... 3 Virtualization Approaches .................................................................................................................... 4 Virtualization for Server Consolidation and Containment ........................................................... 7 How Virtualization Complements New-Generation Hardware .................................................. 8 Para-virtualization ................................................................................................................................... 8 VMware’s Virtualization Portfolio ........................................................................................................ 9 Glossary ..................................................................................................................................................... 10 2
- 3. VMWARE WHITE PAPER Virtualization Overview Introduction Virtualization in a Nutshell Among the leading business challenges confronting CIOs and Simply put, virtualization is an idea whose time has come. IT managers today are: cost-effective utilization of IT infrastruc- The term virtualization broadly describes the separation of a ture; responsiveness in supporting new business initiatives; resource or request for a service from the underlying physical and flexibility in adapting to organizational changes. Driving delivery of that service. With virtual memory, for example, an additional sense of urgency is the continued climate of IT computer software gains access to more memory than is budget constraints and more stringent regulatory requirements. physically installed, via the background swapping of data to Virtualization is a fundamental technological innovation that disk storage. Similarly, virtualization techniques can be applied allows skilled IT managers to deploy creative solutions to such to other IT infrastructure layers - including networks, storage, business challenges. laptop or server hardware, operating systems and applications. This blend of virtualization technologies - or virtual infrastruc- ture - provides a layer of abstraction between computing, storage and networking hardware, and the applications running on it (see Figure 1). The deployment of virtual infrastructure is non-disruptive, since the user experiences are largely unchanged. However, virtual infrastructure gives administrators the advantage of managing pooled resources across the enter- prise, allowing IT managers to be more responsive to dynamic organizational needs and to better leverage infrastructure investments. ����������� ����������� ����������� ���������������� ���������������� ���������������� ��������������������������� ���������������� ���������������� ��� ������ ��� ���� ��� ������ ��� ���� Before Virtualization: After Virtualization: • Single OS image per machine • Hardware-independence of operating • Software and hardware tightly coupled system and applications • Running multiple applications on same machine • Virtual machines can be provisioned to any often creates conflict system • Underutilized resources • Can manage OS and application as a single unit by encapsulating them into virtual • Inflexible and costly infrastructure machines Figure 1: Virtualization 3
- 4. VMWARE WHITE PAPER Using virtual infrastructure solutions such as those from Virtualization Approaches VMware, enterprise IT managers can address challenges that While virtualization has been a part of the IT landscape for include: decades, it is only recently (in 1998) that VMware delivered • Server Consolidation and Containment – Eliminating ‘server the benefits of virtualization to industry-standard x86-based sprawl’ via deployment of systems as virtual machines (VMs) platforms, which now form the majority of desktop, laptop and that can run safely and move transparently across shared server shipments. A key benefit of virtualization is the ability to hardware, and increase server utilization rates from 5-15% run multiple operating systems on a single physical system and to 60-80%. share the underlying hardware resources – known as partition- • Test and Development Optimization – Rapidly provisioning ing. test and development servers by reusing pre-configured Today, virtualization can apply to a range of system layers, systems, enhancing developer collaboration and standard- including hardware-level virtualization, operating system- izing development environments. level virtualization, and high-level language virtual machines. • Business Continuity – Reducing the cost and complexity of Hardware-level virtualization was pioneered on IBM mainframes business continuity (high availability and disaster recovery in the 1970s, and then more recently Unix/RISC system vendors solutions) by encapsulating entire systems into single files began with hardware-based partitioning capabilities before that can be replicated and restored on any target server, moving on to software-based partitioning. thus minimizing downtime. For Unix/RISC and industry-standard x86 systems, the two • Enterprise Desktop – Securing unmanaged PCs, work- approaches typically used with software-based partitioning are stations and laptops without compromising end user hosted and hypervisor architectures (See Figure 2). A hosted autonomy by layering a security policy in software around approach provides partitioning services on top of a standard desktop virtual machines. operating system and supports the broadest range of hardware configurations. In contrast, a hypervisor architecture is the first layer of software installed on a clean x86-based system (hence it is often referred to as a “bare metal” approach). Since it has direct access to the hardware resources, a hypervisor is more efficient than hosted architectures, enabling greater scalability, robustness and performance. ����������� ����������� ���������� ��� ��� ��� ��� ���������������������� �������� ���������� ���������� ���������� ���������� ������� ������ ������ ������ ������ ������� �������������������� ��������������������� ��������������������������� ���������������� ���������������� ��� ������ ��� ���� ��� ������ ��� ���� Hosted Architecture Bare-Metal (Hypervisor) Architecture • Installs and runs as an application • Lean virtualization-centric kernel • Relies on host OS for device support • Service Console for agents and helper and physical resource management applications Figure 2: Virtualization Architectures 4
- 5. VMWARE WHITE PAPER Hypervisors can be designed to be tightly coupled with operat- ing systems or can be agnostic to operating systems. The latter approach provides customers with the capability to implement an OS-neutral management paradigm, thereby providing further rationalization of the data center. Application-level partitioning is another approach, whereby many applications share a single operating system, but this offers less isolation (and higher risk) than hardware or software partitioning, and limited support for legacy applications or heterogeneous environments. However, various partitioning techniques can be combined, albeit with increased complexity. Hence, virtualization is a broad IT initiative, of which partitioning is just one facet. Other benefits include the isolation of virtual machines and the hardware-independence that results from the virtualization process. Virtual machines are highly portable, and can be moved or copied to any industry-standard (x86- based) hardware platform, regardless of the make or model. Thus, virtualization facilitates adaptive IT resource management, and greater responsiveness to changing business conditions (see Figures 3-5). To provide advantages beyond partitioning, several system resources must be virtualized and managed, including CPUs, main memory, and I/O, in addition to having an inter-partition resource management capability. While partitioning is a useful capability for IT organizations, true virtual infrastructure delivers business value well beyond that. ����������� ����������� ����������� ���������������� ���������������� ���������������� ���������������� ���������������� ���������������� ������� ������� ������� ������� ������� ������� ������� Figure 3: Traditional Infrastructure 5
- 6. VMWARE WHITE PAPER Hardware/Software Separation ����������� �������� ��� ��� ������ ������������� ���������� ������ ������ ����� ����� ������ ���������� ������ ���������������������� ������� ������� ������� Figure 4: Virtual Infrastructure Infrastructure is what ����������� ����������� ����������� connects resources to your business. ���������������� ���������������� ���������������� Virtual Infrastructure is a dynamic mapping of your ��������������� ��������������� ��������������� resources to your business. Result: decreased costs and ���������������������� increased efficiencies and responsiveness ������� ������� ������� ������� ������� ������� Transforms farms of individual x86 servers, storage, and networking into a pool of computing resources Figure 5: VMware Virtual Infrastructure 6
- 7. VMWARE WHITE PAPER Virtualization for Server Consolidation and higher management costs. Virtual infrastructure enables Containment more effective optimization of IT resources, through the standardization of data center elements that need to be Virtual infrastructure initiatives often spring from data center managed. server consolidation projects, which focus on reducing existing infrastructure “box count”, retiring older hardware or life-extend- Partitioning alone does not deliver server consolidation or ing legacy applications. Server consolidation benefits result containment, and in turn consolidation does not equate to from a reduction in the overall number of systems and related full virtual infrastructure management. Beyond partition- recurring costs (power, cooling, rack space, etc.) ing and basic component-level resource management, a core set of systems management capabilities are required While server consolidation addresses the reduction of existing to effectively implement realistic data center solutions (see infrastructure, server containment takes a more strategic view, Figure 6). These management capabilities should include leading to a goal of infrastructure unification. Server contain- comprehensive system resource monitoring (of metrics such ment uses an incremental approach to workload virtualization, as CPU activity, disk access, memory utilization and network whereby new projects are provisioned with virtual machines bandwidth), automated provisioning, high availability and rather than physical servers, thus deferring hardware purchases. workload migration support. It is important to note that neither consolidation nor contain- ment should be viewed as standalone exercise. In either case, the most significant benefits result from adopting a total cost- of-ownership (TCO) perspective, with a focus on the ongoing, recurring support and management costs, in addition to one- time, up-front costs. Data center environments are becoming more complex and heterogeneous, with correspondingly VM VM VM VM VMotion VMM VMM VMM VMM Monitor Management Provisioning VirtualCenter Virtual and Consolidated Backup Resource VMFS Networking Enterprise-Class Distributed Management Other Enterprise Features Virtualization DRS MPIO Features Services DAS CPU MMU I/O Distributed Virtualization Virtualization Virtualization Hypervisor Services ESX Server Blade Hardware Hardware CPU Memor y NIC Disk Other Hardware Certification Hardware Figure 6: Virtual Infrastructure Management 7
- 8. VMWARE WHITE PAPER How Virtualization Complements New- Para-virtualization Generation Hardware Although virtualization is rapidly becoming mainstream tech- Extensive ‘scale-out’ and multi-tier application architectures are nology, the concept has attracted a huge amount of interest, becoming increasingly common, and the adoption of smaller and enhancements continue to be investigated. One of these is form-factor blade servers is growing dramatically. Since the para-virtualization, whereby operating system compatibility is transition to blade architectures is generally driven by a desire traded off against performance for certain CPU-bound applica- for physical consolidation of IT resources, virtualization is an tions running on systems without virtualization hardware assist ideal complement for blade servers, delivering benefits such as (see Figure 7). The para-virtualized model offers potential perfor- resource optimization, operational efficiency and rapid provi- mance benefits when a guest operating system or application sioning. is ‘aware’ that it is running within a virtualized environment, The latest generation of x86-based systems feature processors and has been modified to exploit this. One potential downside with 64-bit extensions supporting very large memory capaci- of this approach is that such modified guests cannot ever be ties. This enhances their ability to host large, memory-intensive migrated back to run on physical hardware. applications, as well as allowing many more virtual machines to In addition to requiring modified guest operating systems, para- be hosted by a physical server deployed within a virtual infra- virtualization leverages a hypervisor for the underlying technol- structure. The continual decrease in memory costs will further ogy. In the case of Linux distributions, this approach requires accelerate this trend. extensive changes to an operating system kernel so that it can Likewise, the forthcoming dual-core processor technology coexist with the hypervisor. Accordingly, mainstream Linux significantly benefits IT organizations by dramatically lowering distributions (such as Red Hat or SUSE) cannot be run in a para- the costs of increased performance. Compared to traditional virtualized mode without some level of modification. Likewise, single-core systems, systems utilizing dual-core processors will Microsoft has suggested that a future version of the Windows be less expensive, since only half the number of sockets will be operating system will be developed that can coexist with a new required for the same number of CPUs. By significantly lowering hypervisor offering from Microsoft. the cost of multi-processor systems, dual-core technology will Yet para-virtualization is not an entirely new concept. For accelerate data center consolidation and virtual infrastructure example, VMware has employed it by making available as projects, an option enhanced device drivers (packaged as VMware Beyond these enhancements, VMware is also working closely Tools) that increase the efficiency of guest operating systems. with both Intel and AMD to ensure that new processor technol- Furthermore, if and when para-virtualization optimizations are ogy features are exploited by virtual infrastructure to the fullest eventually built into commercial enterprise Linux distributions, extent. In particular, the new virtualization hardware assist VMware’s hypervisor will support those, as it does all main- enhancements (Intel’s “VT” and AMD’s “Pacifica”) will enable stream operating systems. robust virtualization of the CPU functionality. Such hardware virtualization support does not replace virtual infrastructure, but allows it to run more efficiently. ����������� ����������� ��������������������� ��������������������� ���������������� ���������������� �������������� ������������ Figure 7: Para-virtualization 8
- 9. VMWARE WHITE PAPER VMware’s Virtualization Portfolio VMware is the only provider of high-performance virtualization products that give customers a real choice in operating systems. VMware pioneered x86-based virtualization in 1998 and VMware supports: Windows 95/98/NT/2K/2003/XP/3.1/MS-DOS continues to be the innovator in that market, providing the 6; Linux (Red Hat, SUSE, Mandrake, Caldera); FreeBSD (3.x, 4.0- fundamental virtualization technology for all leading x86- 4.9); Novell (NetWare 4,5,6); Sun Solaris 9 and 10 (experimental). based hardware suppliers. The company offers a variety of software-based partitioning approaches, utilizing both hosted VMware is designed from the ground up to ensure compatibil- (Workstation and VMware Server) and hypervisor (ESX Server) ity with customers’ existing software infrastructure investments. architectures. (see Figure 8) This includes not just operating systems, but also software for management, high availability, clustering, replication, multi- VMware’s virtual machine (VM) approach creates a uniform pathing, and so on. hardware image – implemented in software – on which oper- ating systems and applications run. On top of this platform, VMware’s hypervisor-based products and solutions have been VMware’s VirtualCenter provides management and provisioning running at customer sites since 2001, with more than 75% of of virtual machines, continuous workload consolidation across customers running ESX Server in production deployments. As physical servers and VMotion™ technology for virtual machine the clear x86 virtualization market leader, VMware is uniquely mobility. positioned to continue providing robust, supportable, high- performance virtual infrastructure for real-world, enterprise data VirtualCenter is virtual infrastructure management software that center applications. centrally manages an enterprise’s virtual machines as a single, logical pool of resources. With VirtualCenter, an administra- tor can manage thousands of Windows NT, Windows 2000, Windows 2003, Linux and NetWare servers from a single point of control. Unique to VMware is the VMotion technology, whereby live, running virtual machines can be moved from one physical system to another while maintaining continuous service avail- ability. VMotion thus allows fast reconfiguration and optimiza- tion of resources across the virtual infrastructure. App App p App App OS OS OS OS CONSISTENT VIRTUAL HARDWARE PLATFORM VMware Open Interfaces Infrastructure ACE Workstation VMware Server ESX Server Secured Enterprise Technical Departmental Enterprise Desktop Desktop Computing Computing Mgmt Server, System Architecture Hosted on Windows Hosted on Windows Hosted on Windows Bare Metal Console & APIs & Highlights or Linux or Linux V-SMP Option VMotion Figure 8: Single Virtual Platform Desktop to Enterprise 9
- 10. VMWARE WHITE PAPER Glossary Operating system–level virtualization In this case the virtualization layer sits between the operating Virtual Machine system and the application programs that run on the operating A representation of a real machine using software that provides system. The virtual machine runs applications, or sets of applica- an operating environment which can run or host a guest oper- tions, that are written for the particular operating system being ating system. virtualized. Guest Operating System High-level language virtual machines An operating system running in a virtual machine environment In high-level language virtual machines, the virtualization layer that would otherwise run directly on a separate physical system. sits as an application program on top of an operating system. The layer exports an abstraction of the virtual machine that can Virtual Machine Monitor run programs written and compiled to the particular abstract Software that runs in a layer between a hypervisor or host oper- machine definition. Any program written in the high-level ating system and one or more virtual machines that provides language and compiled for this virtual machine will run in it. the virtual machine abstraction to the guest operating systems. With full virtualization, the virtual machine monitor exports a For more information: virtual machine abstraction identical to a physical machine, so that standard operating systems (e.g., Windows 2000, Windows http://www.vmware.com Server 2003, Linux, etc.) can run just as they would on physical http://www.vmware.com/solutions/ hardware. http://www.vmware.com/vinfrastructure/ Hypervisor A thin layer of software that generally provides virtual partition- ing capabilities which runs directly on hardware, but under- neath higher-level virtualization services. Sometimes referred to as a “bare metal” approach. Hosted Virtualization A virtualization approach where partitioning and virtualization services run on top of a standard operating system (the host). In this approach, the virtualization software relies on the host operating system to provide the services to talk directly to the underlying hardware. Para-virtualization A virtualization approach that exports a modified hardware abstraction which requires operating systems to be explicitly modified and ported to run. Virtualization Hardware Support Industry standard servers will provide improved hardware support for virtualization. Initial hardware support includes processor extensions to address CPU and some memory virtualization. Future support will include I/O virtualization, and eventually more complex memory virtualization management. Hardware-level virtualization Here the virtualization layer sits right on top of the hardware exporting the virtual machine abstraction. Because the virtual machine looks like the hardware, all the software written for it will run in the virtual machine. 10
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