Virtualization is a technology that subdivides the resources of modern computers. Modern computers are sufficiently powerful to allow multiple smaller servers to run on a single physical machine. There are a few challenges that must be overcome for successful virtualization. First and foremost, the multiple smaller servers must be isolated from one another so that issues with one server don't affect the other servers. Secondly, multiple operating systems must be supported. Last but not least, performance overhead introduced by virtualization should be small.
A great solution to this is Microsoft Virtual Server 2005. It successfully addresses all three challenges. This product allows you to run multiple self-contained operating systems simultaneously on a single physical server. Each of these instances is known as a Virtual Machine. The total number of Virtual Machines that can run simultaneously varies greatly depending on the resources of the physical server, but there is a maximum of 64 Virtual Machines per Virtual Server. The physical server is commonly referred to as the host.
There are currently two editions of Virtual Server 2005: Standard Edition and Enterprise Edition. The only difference between the editions is that the Standard Edition supports up to four processors on the host and the Enterprise Edition supports up to 32 processors on the host. A consideration needs to be made regarding the host operating system when planning the total processors and memory. Windows Server 2003 Standard Edition supports up to 4 GB of RAM and 2 processors, Enterprise Edition supports up to 32 GB of RAM and 8 processors, and Datacenter Edition supports up to 64 GB of RAM and a minimum of 8 to 32 processors.
Some of the key benefits of virtualization include running testing and production applications on the same physical server, hosting legacy applications, and consolidating multiple servers. Prior to virtualization, these tasks required numerous physical machines, increasing overhead and therefore the Total Cost of Ownership (TCO).
Virtual Server 2005 has a comprehensive Component Object Model Application Program Interface (COM API) that allows you to have extensive control of the Virtual Machines through scripting. And of course, since it is based on COM, you can use a variety of languages to accomplish this. Virtual Server also has events that can be used to trigger scripts to run.
Management is easily accomplished through an administration web interface. Virtual Machines also offer full Active Directory integration. If you are using Microsoft Operations Manager 2005, there is a management pack available for Virtual Server for enhanced management features.
Virtual Server 2005 can be installed on all editions of Windows Server 2003, including Small Business Server 2003 Standard and Enterprise Editions. It can also be installed on Windows XP Professional for non-production use. Note that Virtual Server 2005 doesn't run on any version of Windows 2000. The Virtual Machines can run nearly all x86-based server operating systems, however Microsoft Product and Support Services (PSS) only supports all versions of Windows Server 2003, Windows Server 2000, and Windows NT 4.0 with Service Pack 6a.
The installation is quite simple and straightforward. You can have Virtual Server up and running in just minutes by executing the installation package and following the prompts. Here are some configuration settings to be aware of in regards to the host server:
- Disable the offload features on the host Network Interface Card (NIC)
- Leaving this enabled often shows up as an attempted Denial of Service (DOS) attack and leads to decreased network performance
- Virtual Server does not support teamed NICS
- Disable CPU hyperthreading on the host machine
- CPU hyperthreading will actually degrade performance
- Do not use the /3Gb switch in the host boot.ini
- Using this switch will cause out of memory errors.
ORCS Web is taking advantage of virtualization technologies to provide cost effective solutions to dedicated hosting. Point your browser to www.orcsweb.com for more information.
In Part II of this series on Virtualization, the topic will be about setting up Virtual Machines. This will include undocumented features and some things to be aware of.
Microsoft newsgroups: microsoft.public.virtualserver
Rick Barber is a support specialist with ORCS Web, Inc. - a company that provides managed hosting services for clients who develop and deploy their applications on Microsoft Windows platforms.