With one new product released, and one about to be, server virtualisation is becoming a reality in the low-end server space. How can virtual servers help you?
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Contents 
MS Virtual Server 2005
VMware GSX Server 3
Specifications
How we tested
Editor's choice
About RMIT |
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At first glance, much like a workstation, it's convenient to run two or more operating systems simultaneously on the one server hardware platform. You might for example have a single server running a virtual Windows Server and Exchange for your mail, while you have a second virtual Web server running Linux and Apache. You have the ease and convenience of Exchange and the security and robustness of Linux and Apache running on the same piece of hardware.
Depending on your requirements, this alone may save money as a modestly more powerful server can be considerably less expensive than two less powerful servers, and the management and resources required by the single server will also be less.
Now imagine the savings that would be possible across an entire enterprise with multiple environments and workloads existing on substantially fewer servers. Of course you will certainly want peace of mind that should a virtual server hang, it doesn't upset the entire applecart and impact on any of the other virtual servers running on the host hardware.
One of the key drivers for server virtualisation is the fact that the vast majority of servers are chronically underutilised. This is because servers are most often commissioned to cater to a peak load that may only be a couple of hours a day or at the end of the month. Under normal loading, these additional resources sit idle. With virtualisation, wasted resources can be put to better use by running other tasks.
In addition, server consolidation is made a great deal easier by virtualisation. You could theoretically take a large number of older servers and run them on a single, virtualised box. Indeed one of the reasons behind Microsoft's push towards server virtualisation is the large number of customers still running Windows NT 4.0, which Microsoft will stop supporting at the end of this year. Microsoft is hoping virtualisation and consolidation combined will be a strong driver to finally wean those companies off their old NT 4.0 servers.
To ensure sensible resource allocation of the host hardware there must be some way to tune each virtual server in terms of CPU and memory resource allocation.
Under a virtualised environment, administrators want to be sure that when peaks do occur, the system will be able to throttle back the other tasks and provide enough resources for the task that requires peak performance, while the servers are all still running. This ability to dynamically adjust to virtual server loading is now emerging in high-end Unix systems such as IBM's AIX 5.3 and Sun's soon-to-be-released Solaris 10. The current virtualisation software for x86 servers only allows most of these resource adjustments to occur by rebooting the virtual server.
Admins may also want to assign specific NICs and drives or drive partitions to each virtual server. An alternative there is to virtualise the network and storage layers as well; this feature is better catered for in high-end Unix systems, but is available in the products we reviewed.
One benefit that may not spring directly to mind is that your multiple virtual servers all think they're running on the same generic hardware, no matter what physical host hardware the virtual servers reside on. It would be a great deal easier to create a standard server image on the virtual machine's hardware and only have to worry about driver issues when installing a new physical server. The administrative savings across a large enterprise could be significant.
While on the topic of administration, think of the advantages for disaster recovery. For example, imagine three critical servers that must never go down. Under normal circumstances you may need to have another three redundant servers to ensure business continuation should one of the primary servers fail. With virtual servers, you could run a redundant virtual server for Server A on Server B and so on. For added security, you could have a fourth server running all three redundant servers.
But how easy is it to centrally administer a very large infrastructure of virtual servers?
Surprisingly easy, actually. Micrososft's Virtual Server 2005 integrates with Microsoft's management tools and third-party tools, while VMware's Virtual Server GSX has its own virtual infrastructure management software called VirtualCentre and can also integrate with third-party tools.
Another advantage of the generic hardware of the virtual environment is that there are virtual hardware drivers for a wide range of operating systems. So if your company is stuck with an old legacy application that only runs on NT4, this can be a boon. Trying to find drivers for your shiny new server hardware for many of the older operating systems is nigh impossible, but the virtual environment can cater for NT4 without any problems at all.
3%
5%
Your excellent web article refers to your test results which i can't find a link to anywhere in the article.
As the test results are referenced as being "on on page 86, I guess this is an oversight.
Could you provide the URL to the test results?
Many thanks,
Ravi cabral