Advanced Virtualization Benefits of Windows Server 2008 Editions for the Enterprise
White Paper
Published: February 2008
For the latest information, please see www.microsoft.com/windowsserver2008/virtualization/default.mspx
Contents
1
Introduction 1
Advanced Virtualization Key Features and Benefits 2
New licensing features 2
Quick Migration 4
Clustering 4
General Virtualization Features and Benefits 5
64-bit support for hosts and guests 5
Optimized virtual machine access to physical resources via hypervisor 5
Processor-assisted virtualization 6
Multiprocessor support for hosts and guests 6
Redesigned I/O architecture for better performance 6
Easy upgrade and migration 6
Support for non-Microsoft guest operating systems 7
System Center Virtual Machine Manager 7
Other new and enhanced features 8
Common Usage Scenarios 9
Production server consolidation 9
Business continuity management 10
Dynamic data center 11
Software test and development 11
Summary 13
Related Links 14
Introduction
IT departments today are under increasing pressure to manage and support expanding computer resources, while at the same time reducing costs. Server virtualization, which enables multiple virtual machines (VMs) to run concurrently on the same physical server, has become a broadly accepted method to meet these requirements. By converting underutilized physical servers into virtual machines that run on a single physical server, organizations can reduce space and hardware costs in the data center. Also, because virtual machines are generally much faster to recover in a disaster than are physical computers, virtualization also increases server uptime and reliability.
As a result, IDC predicts that the virtualization services market will grow from $5.5 billion in 2006 to $11.7 billion in 2011, as data center managers struggle to address power and cooling issues and the need for increased capacity.[1]
In response to these developments, Microsoft has introduced advanced virtualization features in Windows Server® 2008 via Windows Server Hyper-V™, a next-generation, 64-bit virtualization technology that facilitates agility and seamless management of both physical and virtual components. As a key part of any server consolidation strategy, solutions leveraging Windows Server Hyper-V increase hardware utilization and allow organizations to rapidly configure and deploy new servers.
To make virtual machine management even easier and more efficient, Microsoft has also introduced Microsoft® System Center Virtual Machine Manager 2007, which improves operational efficiency by reducing the amount of time required to manage individual servers and migrate physical computers to virtual machines.
Finally, Microsoft has simplified the licensing use rights in Windows Server® 2008 Enterprise and Windows Server® 2008 Datacenter, making deploying virtual machines less expensive and simplifying the management guest operating system licenses.
The key value propositions that the virtualization capabilities in Windows Server 2008 enables are as follows:
· Server consolidation reduces the total quantity and cost of server ownership by maximizing hardware utilization, consolidating workloads, and reducing management costs.
· Business continuity management eliminates the impact of scheduled and unscheduled downtime, and enables disaster recovery abilities with features such as Quick Migration and clustering.
· Development and test environments create a more flexible and easy-to-manage environment that maximizes test hardware, reduces costs, and improves life cycle management and test coverage.
· Dynamic data center leverages the benefits of virtualization to create a more agile infrastructure combined with new management capabilities, allowing you to move virtual machines without impacting users.
This white paper describes the benefits of advanced virtualization features in Windows Server 2008 and outlines common scenarios in which they can save organizations time and money. It also explains the new licensing use rights of Windows Server 2008 Enterprise and Datacenter that simplify license management and reduce the cost of licensing guest operating systems.
Advanced Virtualization Key Features and Benefits
This section reviews the key features and benefits of Windows Server Hyper-V in Windows Server 2008 Enterprise and Windows Server 2008 Datacenter.
New licensing features
Simplified licensing in Windows Server 2008 Enterprise and Datacenter allow customers to run multiple instances of the software on the same physical server under a single license. This saves you money on licensing costs and makes it easier to keep track of guest operating system licenses.
Windows Server 2008 Enterprise licensing
To help you take advantage of the server consolidation benefits that virtualization offers, a single license for Windows Server 2008 Enterprise allows you to run multiple instances of the operating system on a server. Each Windows Server 2008 Enterprise license assigned to a server allows you to run one instance in the physical host operating system, and up to four instances of guest Windows Server 2008 Enterprise operating systems on that server. In addition, you may run instances of Windows Server® 2008 Standard in place of the instances of Windows Server 2008 Enterprise as the guest operating systems. For example, in the following figure, Server A is running five separate instances of Windows Server 2008. The host operating system of Server A is running an instance of Windows Server 2008 Enterprise. Two guest operating systems of Server A are running instances of Windows Server 2008 Standard, and two are running instances of Windows Server 2008 Enterprise. By assigning a Windows Server 2008 Enterprise license to Server A, you may run all five instances on Server A under that single license.
Figure 1 Windows Server 2008 Enterprise allows you to run up to five instances on a server
The expanded use rights for Windows Server 2008 Enterprise do not impact the licensing for Windows Server 2008 Standard. Each license for Windows Server 2008 Standard allows you to run one instance on that server.
Windows Server 2008 Datacenter licensing
To help you take further advantage of the server consolidation benefits that virtualization offers, Windows Server 2008 Datacenter allows you to run any number of instances of the software on a server, as described in this section. Each server must be licensed by physical processors—you need a license for each physical processor on a particular server. (The number of virtual processors used by a virtual hardware system is not relevant to the licensing of Windows Server 2008 Datacenter.) Once you have determined the number of licenses required, you must assign those licenses to the server. Once the server is assigned the correct number of licenses, you may run, at any one time:
· One instance of the server software in the physical operating system environment (the host operating system)
-- and --
· Any number of instances of the server software in virtual operating system environments
In addition, you may run instances of Windows Server 2008 Standard or Enterprise in place of Windows Server 2008 Datacenter as the guest operating systems. For example, in the following figure, Server A is running ten separate instances of Windows Server 2008 in ten separate operating systems. The host operating system of Server A is running an instance of Windows Server 2008 Datacenter. Three virtual machines of Server A are running instances of Windows Server 2008 Standard, three are running instances of Windows Server 2008 Enterprise, and three are running instances of Windows Server 2008 Datacenter.
Figure 2 Windows Server 2008 Datacenter allows you to run an unlimited number of
instances on a server
The expanded use rights for Windows Server 2008 Datacenter do not impact the licensing for Windows Server 2008 Standard. Each license for Windows Server 2008 Standard allows you to run one instance on that server.
Note that Windows Server 2008 for Itanium-Based Systems includes the same rights to run an unlimited number of virtual instances. However, Hyper-V is not available for Itanium, so a third-party virtualization product or technology would be required to make use of these rights. Several companies have announced such products.
Note that although it is licensed by physical processor, Windows Server 2008 Client Access Licenses (CALs) are still required for access to instances of Windows Server 2008 Datacenter.
Quick Migration
Quick Migration provides the ability to move a virtual machine from one host computer to another in the same server cluster with minimal disruption. You can use Quick Migration for making planned moves as well as managing unplanned server downtime. In the event of planned moves, Quick Migration can be used to move running virtual machines to another cluster node. In the event of unplanned downtime, the Cluster service automatically restarts all virtual machines on a surviving cluster node. This capability provides high availability and flexibility to achieve an agile and dynamic data center.
Quick Migration requires the Windows Server 2008 failover clustering role to be added and configured on the host servers running Windows Server Hyper-V. Because of this, Quick Migration is only available with Windows Server 2008 Enterprise and Windows Server 2008 Datacenter. In addition, failover clustering requires shared storage for the cluster nodes. This can include an iSCSI or Fiber-Channel Storage Area Network (SAN). All virtual machines are stored in the shared storage area, and the running virtual machine state is managed by one of the Windows Server Hyper-V nodes. The speed of the Quick Migration depends on the amount of information in memory that must be moved and the speed of the shared storage device.
You can implement Quick Migration in any of the following three ways:
· Use System Center Virtual Machine Manager, which provides a graphical user interface for drag-and-drop migration of running virtual machines from one Windows Server 2008 host server to another in the same cluster.
· Use Failover Clusters Manager to initiate the Quick Migration of a running virtual machine from one host server to another in the same cluster with a minimal amount of downtime.
· Use the WMI Provider in Windows Server 2008 to script the Quick Migration of a running virtual machine from one host server to another in the same cluster.
Clustering
Flexible clustering scenarios provide high availability for mission-critical environments while improving patching and hardware maintenance processes. Clustering can be achieved by clustering the Windows Server Hyper-V role itself (host clustering), as described previously in Quick Migration, or by clustering the individual guest operating systems running in virtual machines (guest clustering).
Guest clustering provides high availability for a large variety of resources including databases, file shares, and network infrastructure and application services. Guest clustering can be combined with Windows Server 2008 Network Load Balancing (NLB) services to provide both high availability and load balancing across multiple host servers. NLB is a feature that distributes the load for networked client and server applications across multiple servers in an NLB cluster.
General Virtualization Features and Benefits
This section covers the Windows Server Hyper-V virtualization features available with Windows Server 2008 Standard, Windows Server 2008 Enterprise, and Windows Server 2008 Datacenter.
64-bit support for hosts and guests
Because the Windows Server Hyper-V hypervisor is a 64-bit design, the virtualization role must be run on x64 editions of Windows Server 2008. This 64-bit architecture can address far more memory than virtualization platforms based on 32-bit architectures—up to 2 terabytes of RAM on the host server.
Also, because some applications may be available only in 32-bit versions and some only in 64-bit versions, the hypervisor supports both 32-bit and 64-bit guest operating systems. Both 32-bit and 64-bit virtual machines can run alongside each other on the same host server.
Support for 64-bit guests enables organizations to virtualize more applications that are memory-intensive and benefit from the increased memory pool accessible in a 64-bit environment, providing nearly unlimited scalability for virtual machines. Virtual machines hosted by Windows Server Hyper-V can be assigned up to 64 gigabytes (GB) of RAM each. Moreover, because both Windows Server 2008 Enterprise and Windows Server 2008 Datacenter both support up to 2 terabytes of RAM on the host server, this can provide more total memory for use by virtual machines.
Virtual machines also benefit from resource allocation features, in which a variable amount of RAM is assigned to each virtual machine based on its current resource needs. With this flexibility in resource assignment, multiple guest operating systems can be consolidated on a single host, each running with little compromise in efficiency.
Optimized virtual machine access to physical resources via hypervisor
Windows Server Hyper-V uses a 64-bit hypervisor to provide a secure and robust base for virtualization solutions. The hypervisor is a thin layer of software that resides between the operating system and the hardware. It allows multiple virtual machines to access physical memory and CPU resources without conflicts. The hypervisor leverages Windows Server driver support together with hardware-assisted virtualization technology that includes processors using Intel VT and AMD-VT technology. As a result, the Windows Server Hyper-V hypervisor enables high performance and scalability for guest operating systems.
Windows Server Hyper-V hypervisor also enhances security. It incorporates the same design principles as microkernel operating systems. In particular, operating system drivers and other components that are exposed to attack are executed at a less privileged level, meaning that a component malfunction or attack results in limited or no damage to the kernel.
The hypervisor uses a similar design approach to achieve a minimal Trusted Computing Base (TCB), which incorporates no drivers of its own (these are contained in the parent and child partitions). This microkernelized hypervisor architecture provides a more stable, secure foundation for running virtual machines, especially when compared to virtualization platforms based on a monolithic hypervisor—one that incorporates hardware drivers into the hypervisor codebase.
Processor-assisted virtualization
Collaboration between hardware virtualization features and the software virtualization components of Windows Server 2008 creates a high-performance virtualization platform. Because the Windows Server Hyper-V hypervisor takes advantage of Intel VT and AMD-V technology, more of the work of supporting multiple guest operating systems is performed by system hardware, and less needs to be performed by the virtualization stack and hypervisor.
Virtualization platforms that rely on the software emulation of hardware must frequently interrupt guest operating systems by performing on-the-fly translation of hardware requests into a form that is compatible with the virtualization environment. Intel VT- and AMD-V-enabled processors render much of this on-the-fly translation unnecessary by incorporating virtualization extensions to x86 architecture. This means that virtualization platforms that are designed for these technologies have lower overhead, and virtual machines run more efficiently.
Multiprocessor support for hosts and guests
Windows Server Hyper-V provides the capability to allocate multiple CPU resources to a single virtual machine and enables virtualization of multithreaded applications. It also adds dynamic CPU allocation features. This capability, combined with support for 64-bit guests and up to 64 processors available in Windows Server 2008 Datacenter, makes Windows Server Hyper-V a scalable platform for virtualization.