Introduction: VMWare Virtualization and Web Hosting
Up to this point most web hosting businesses are still using dedicated servers with local disk storage to provide a hosting platform for their customers. Some of the bigger web hosting businesses use SAN connected servers and centralized storage, but almost nobody uses virtualization products to do web hosting. What is virtualization and how can a web hosting business benefit from VMWare virtualization? Server virtualization is a technology where servers and server hardware are mapped to each other via software, but where the actual hardware association is hidden to the user. Virtualization is the technique of managing and presenting storage devices and server resources regardless of their physical layout or location. In case of server virtualization the actual host server (physical server) hosts several virtual servers on top of the actual operating system. The host server presents the hardware resources to the VMs.
VMWare is currently the market leader in regards to virtualization technology. The VMWare Infrastructure ESX product is a stripped Linux operating system with a (now) build-in sophisticated virtualization technology. The software does a great job of dynamically mapping physical resources like memory and CPU to virtual counterparts within virtual server machines (VMs). Virtualization technology uses the fact that most physical servers are under-utilized in regards to CPU and memory usage. On average most application servers are using less than 10% of their physical resources. The remaining 90% are paid for, but will never be used. What a waste of money you might think. Now take virtualization and base your resource allocation on the fact mentioned before. Take one beefed up physical server and make it home to 10 or even 20 virtual machines. The initial higher cost for more memory and disk space will easily be made up for by the number of server you can present on top of this one physical server. Less hardware to maintain, less support contracts to pay for, less heat in your data center, and less electricity used.
Take this a step further and combine several physical servers into a farm-style environment and take advantage of VMWare’s virtualization products. Live migrate VMs from one host server to another without any visible interruption for the user. Yes, you heard that right. You move a virtual server while it is running from one physical host to another and the user who is visiting websites on that server does not notice a single drop in accessibility or performance.
Example 1: Host server A has a hardware problem and you move the VMs off (while they are running) to the other servers in your VMWare farm. You take Host A down and replace the faulty hardware. Once it is up you move the VMs back to they were before and again with no interruption to the user.
Example 2: A website on a virtual server (VM) was mentioned on CNN and ABC News and gets flooded with millions of HTTP requests. This website and the underlying virtual server suddenly need all available memory and CPU resources. The web host moves other VMs off the physical host to have enough resources available. Still not enough. Shutdown the VM and on the fly the web host adds more (virtual) RAM and a couple more (virtual) CPUs. The VM is back online within 5 minutes and all is well. Try to do that with a physical server.
Of course there is a lot more about how VMWare and their virtualization products can fit perfectly into a web hosting business. Read the other articles here on “The Web Hosting Resource Kit”.