Server virtualization means running multiple virtual servers on one piece of physical server hardware. The idea being that each server wastes a lot of its resources (CPU, RAM, etc). With virtualization, the leftover resources can be used to run more virtual servers. On one physical server, how many virtual servers can you run? Two? Ten? Fifty? The answer is... Yes.
Virtualization is built on three main elements: servers, storage (disks), and virtualization software called the hyper-visor. The hyper-visor is the operating system that gets installed on the physical server (known as the host), and allows you to build virtual Windows and Linux servers (known as guests, virtual machines or VMs) on top. There are a number of hyper-visors available including VMware vSphere ESXi, Microsoft Hyper-V, Citrix XenServer, and RedHat KVM, among others. Basic versions of these hyper-visors are available for free, while premium versions and add-on products with additional scalability and management features are also available.
The Basic Kit
The simplest virtualization design is a single host, running a free hyper-visor, with internal storage. This can be done cheaply, for a few thousand dollars, and can be built to run perhaps half a dozen virtual servers or more. The number of virtual servers you can run on one physical server will be based on how much CPU, RAM, and disk performance you can put in the box. A good choice for such a box is the DL385 G7 server from Hewlett Packard.
The DL385 G7 can be built with two processors, up to 16 cores each, for a total of 32 cores. That's a lot of processing power in a small server. It can hold up to 512GB of RAM, and up to 18TB of internal disks. Now all that may be a bit much for an SMB, and you may think twice about putting all your eggs in one basket. But these maximums show that you can build this box to the specs you need.
For example, two 8-core processors and 32GB of RAM should be easily enough to run half a dozen virtual servers. Besides processor power and RAM, disk performance will be a determining factor in how many virtual servers your host will be able to run. The DL385 G7 can hold up to 16 disks. More disks means more performance, which means more virtual servers.
To give an idea of just how many VMs you can run, consider a typical server which might have two CPU cores, 4GB RAM, and one or two internal disks. The 16-core, 32GB DL385 G7 mentioned about would be able to run eight of these. Now of course I'm oversimplifying; how busy these VMs are will determine whether your host will be able to handle the load without running into performance bottlenecks.
Here's where a consultant might come in handy. I'm partial to consultants, since I am one. The virtualization consultant can help you determine what your needs are, how much resources are required for the virtual servers you want to run, and how to build the host to meet those requirements.
Of course, your needs might be larger than one host can provide, or you may not want to put your entire business in one host. Well, virtualization scales big, and it scales well. You can build two or more hosts, with shared storage, as a cluster. The cluster can provide fail-over capability so that if a failure occurs, your virtual servers can be automatically restarted on the remaining hosts. But we'll discuss that in another article.
Private Cloud?OK, maybe the title is a little overstated. Cloud is such an over-used buzz word lately. Cloud computing generally means putting your servers, applications or data somewhere out on the Internet (public), hosted in someone else's data center. In those cloud data centers they are surely running your stuff on one of the hyper-visors mentioned above.
The cloud, when used to host VMs, allows you to quickly and easily deploy new servers with a few mouse clicks. It allows you to build up and tear down VMs with relative ease, giving you a new flexibility that physical servers don't provide. Well, building systems at your own office (private) like the ones we've been discussing gives you that same capability, and having your VMs in your own office rather than on the Internet clearly can provide better performance, better security, and lower cost.
For the cost of one DL385 and a free hyper-visor, your business can start virtualizing its servers, start saving big, and start building your own cloud.