Windows Server 2008 : Planning Operating System Virtualization (part 2) - Planning for Server Consolidation

7/13/2011 5:49:58 PM

Candidates for Virtualization

When you are considering server deployment options, it will be advantageous in some situations to deploy a virtualized server rather than the real thing. One factor is cost: a Windows Server 2008 Enterprise license includes the licenses for four hosted virtual instances. Although you need to consider many other costs when making a comparison, from a licensing perspective, one Windows Server 2008 Enterprise license will cost less than five standard licenses. Also remember that server-grade hardware will always cost significantly more than a Windows Server 2008 Enterprise license, especially if your organization has a licensing agreement with Microsoft.

Although each situation will be different, in certain archetypical situations, you would plan a virtualized server rather than a traditional installation, including the following:

  • You want to use WDS at a branch office location for a rollout that will last several days, but you do not have the resources to deploy extra hardware to that location. In this case, you could virtualize a WDS server and turn on the VM only when it was needed. If more operating systems need to be rolled out later, the VM could be turned on.

  • You have two applications hosted on the same server that conflict with each other. Because custom applications do not always work together well, sometimes you need to place each application in its own VM. Applications hosted on separate computers are unlikely to conflict with each other! Another solution is to virtualize the application itself. Virtualizing applications is covered later in this lesson.

  • You are working with developers who need to test an application. If you have worked as a systems administrator in an environment with developers, you know that some projects are not stable until they are nearly complete, and, until that time, they have a nasty habit of crashing the server. Giving developers their own VM to work with allows them to crash a server as often as they like without your worrying about the impact on anyone outside the development group.

Some server deployments make poor candidates for virtualization. Servers that have high I/O requirements or high CPU requirements make poor candidates. A server that monopolizes CPU, memory, and disk resources on a single computer will require the same level of resources when virtualized, and a traditional server installation will provide better performance than running that same server virtualized on the same hardware. In general, you are reasonably safe in deciding to deploy virtual servers if the server does not have a large performance footprint. When a server is expected to have a significant performance footprint, you will need to develop further metrics to decide whether virtualization offers any advantage.

Note: Number of licenses

Remember that Windows Server 2008 Datacenter (x64) has unlimited licenses for virtual hosts and that Windows Server 2008 Enterprise (x64) has only four.

Planning for Server Consolidation

When you plan the deployment of Windows Server 2008 at a particular site that has an existing Windows server infrastructure, you will be making an assessment about which of the existing servers can be virtualized, which need to be migrated, and which need to be upgraded. If you have deployed System Center Operations Manager in your environment, you can use the product to generate a Virtualization Candidates report, which will give you a list of servers in your environment that make excellent candidates for virtualization given their current usage levels.

When you have determined the need to virtualize a server, the next step is to move that server from its existing hardware to a virtualized partition running under Windows Server 2008. You can use two tools to virtualize a server installed on traditional hardware: the Virtual Server Migration Toolkit (VSMT) and SCVMM. Both tools are compatible not only with Hyper-V but also with Virtual Server 2005 R2.

Virtual Server Migration Toolkit

VSMT is the best tool to use when you have a small number of servers that need to be virtualized. The tool is command line–based and uses Extensible Markup Language (XML) files to store configuration data that is used during the migration process. You cannot use the VSMT tool to manage virtualized servers—it is purely a tool for migrating existing servers to a virtualized environment.

Unlike the SCVMM 2007 migration tools, it is not possible to use the VSMT to perform migrations without downtime. The VSMT was primarily designed to migrate servers to the Virtual Server 2005 platform. It is because Virtual Server 2005 virtualized operating systems are compatible with Hyper-V that you can use this tool to perform migrations to Windows Server 2008 virtual hosts.

More Info: More on the Virtual Server Migration Toolkit

To find out more about how you can use VSMT to virtualize servers, see the following TechNet article:

System Center Virtual Machine Manager 2007

You should plan to use SCVMM 2007 when you have a large number of VMs to manage in a single location. SCVMM requires a significant infrastructure investment and is primarily designed to manage enterprise-sized virtual server deployments rather than to be something that you would plan to use to migrate a couple of branch office servers into a virtual environment. If you are planning to virtualize a large number of servers, you will find the extra functionality of SCVMM 2007 manager valuable. Unlike VSMT, SCVMM is fully integrated with Windows PowerShell, giving you more flexibility in migrating servers from physical to virtualized environments.

You should note that deployment of SCVMM requires a connection to a SQL Server database. The Express Edition of SQL Server 2005 SP2 is included with the SCVMM 2007 installation files, or you can use an existing SQL Server 2005 SP2 or SQL Server 2008 instance. SCVMM 2007 uses this database to store VM configuration information.

In addition to virtualizing traditional server installations, you can use SCVMM to do the following:

  • Monitor all of the virtualized servers in your environment. A single SCVMM server can be used to manage up to 8,000 VMs.

  • Monitor all Hyper-V hosts in your environment. A single SCVMM server can be used to manage up to 400 Hyper-V or Virtual Server 2005 R2 host computers.

  • When connected to a Fibre Channel SAN environment, move virtualized servers from one Hyper-V host to another.

  • Move virtualized servers to and from libraries.

  • Delegate permissions so that users with nonadministrative privileges are able to create and manage their own VMs.

  • Migrate servers from physical to virtual without any downtime.

SCVMM 2007 includes capacity planning technology that allows you to assign VMs to the virtual hosts in your environment that have the appropriate available resources to support them based on VM performance data. For example, if you have 10 Windows Server 2008 computers that each host multiple VMs, the capacity planning technology in SCVMM 2007 can make recommendations about where each VM should be deployed based on performance data observations.

SCVMM 2007 increases your operating system virtualization planning options because it includes tools that allow you to make the most efficient use of your VM and virtual host infrastructure. As Figure 4 shows, the capacity planning tools available in SCVMM 2007 can be heavily customized, allowing administrators to prioritize the importance of specific resources. For example, you can configure the capacity planning tools to prioritize servers that have available memory over those that have lower CPU utilization.

Figure 4. Configuring capacity planning

Components of a System Center Virtual Machine Manager 2007 Deployment

An SCVMM 2007 deployment consists of several components that can all be installed on the one server or that can be installed on several servers throughout the enterprise. SCVMM 2007 components include the following:

  • SCVMM server This is the server on which the SCVMM software is installed. You should install this component first. Except under unusual circumstances, there is usually only one SCVMM server in an environment, so you should plan redundancy using failover clustering rather than the deployment of multiple servers. Although it is possible to deploy multiple SCVMM servers in a forest, each SCVMM server requires a separate SCVMM database, although these databases can be hosted on the same SQL Server instance. An SCVMM server cannot be installed in a forest that has a disjointed DNS namespace (multiple separate domain trees within the same forest).

  • SCVMM agent This component is installed on a VM host running Virtual Server 2005 R2 or Hyper-V and SCVMM library servers. To be automatically managed, all VM hosts must be members of the same forest as the SCVMM server. It is possible to install the SCVMM agent on a computer that is not a member of the same forest and configure a connection manually to the SCVMM server. This is usually done when a virtual host is deployed on a perimeter network. A single SCVMM server can manage a maximum of 400 servers running Hyper-V or Virtual Server 2005 R2 SP1, or both. A Hyper-V or Virtual Server 2005 R2 SP1 host can be managed only by a single SCVMM server.

    More Info: Installing SCVMM agent locally

    For more information about installing the SCVMM agent locally, consult the following TechNet document:

  • SCVMM database The SCVMM database can be hosted either on SQL Server 2005 or SQL Server 2008. If no SQL Server instance is specified, the setup routine installs SQL Server Express on the local SCVMM server. The drawback of using SQL Server Express is that the advanced reporting functionality will be unavailable. In addition to using SQL Server 2005 or SQL Server 2008, if you plan to use the advanced reporting functionality of the product, you must also deploy System Center Operations Manager 2007 in the same forest. If the SCVMM database is remote from the SCVMM server, you should secure the connection between the two servers using Secure Sockets Layer (SSL).

    More Info: SCVMM and a remote instance of SQL Server

    For more information on the specific steps involved in configuring a remote instance of SQL Server to support SCVMM 2007, consult the following TechNet document:

  • SCVMM Administrator console Like all management consoles, the SCVMM administrator console can be installed on an administrator workstation to manage SCVMM remotely or used to directly manage the server on which SCVMM components are installed.

  • SCVMM self-service portal This portal allows users who are not SCVMM administrators to manage VMs to which they have been delegated permissions. The portal is Web-based and should be installed on a server that has IIS 6.0 or later and is a member of the same forest as the SCVMM server.

  • SCVMM library server The library is a catalog of resources that are used to create VMs using SCVMM. These resources include ISO images, scripts, hardware profiles, VM templates, virtual hard disks, and stored VMs. A VM template includes a guest operating system profile, a hardware profile, and virtual hard disks. These resources are hosted on a set of shares that are managed through the SCVMM console. The library can be stored across multiple physical servers in an enterprise deployment. If the SCVMM library is not deployed on the VM host server, the network connection between a VM host server and the library it uses should be as fast as possible. A default library share called VMMLibrary is created on the SCVMM server during the installation process unless an administrator determines otherwise. An SCVMM Library server can only be managed by one SCVMM server. You cannot directly share resources between different SCVMM environments.

SCVMM 2007 in the Branch Office

SCVMM 2007 is usually deployed in a datacenter environment, with all components, including VM hosts, located at the same site. If SCVMM 2007 is going to be used to create, run, and manage VMs at branch and satellite offices, you should deploy a VMM library server and a VM host at the branch office site. This will allow you to deploy new VMs directly from the library to the VM hosts without having to transfer gigabytes of data across the organizational wide area network (WAN) link.

In branch office deployments, the SCVMM library is usually deployed on the same server that functions as the VM host. This allows for rapid deployments because the files used to build new VMs do not need to be copied across the network. The drawback of this type of deployment is that it requires a significant amount of hard disk drive space to store both the library data and the deployed VMs.

More Info: More on planning SCVMM 2007 deployment

For more information on planning an SCVMM 2007 deployment, consult the following TechNet Web page:

More Info: SCVMM 2007 webcasts

To learn more about using SCVMM 2007, access the following TechNet webcasts: SCVMM 2007 Overview at and Managing Virtualization at

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