Memory and storage are relatively inexpensive today and are certainly vastly less expensive than purchasing additional server hardware and paying to support it. It is not uncommon for a small business to easily virtualize half a dozen servers on a single piece of hardware at a minimum. And twenty or more is not an unreasonable number to hope to achieve.
Many small shops instantly jump to the conclusion that virtualization requires expensive SAN storage. This is not the case at all. Virtualization provides a range of benefits even without using a SAN storage infrastructure.
There are, of course, some significant advantages available by using SAN in conjunction with virtualization and high availability or load balancing technologies. Often, though, these high availability and load balancing capabilities are additional features that did not exist prior to virtualization and are not necessary in order for a shop to see significant benefits from virtualization. But they do present an opportunity for future improvement when and if budgets allow.
Small businesses will immediately see many advantages from virtualization, even doing so on a small scale. Some of these benefits are obvious and some are less so.
Cost: Our first advantage is hardware cost. By eliminating the need to purchase and support expensive server hardware on a per operating system basis we can now deploy more systems at lower cost per system. In many cases this is not only a cost savings but will also provide greater funds necessary to move from more spartan servers into fewer but more enterprise class offerings with important performance, stability and support features. These features may include integrated power management and KVM over IP from an out-of-band management console.
Reducing power consumption: It is very trendy, and for good reason, for companies to be concerned with how "green" they are today and IT virtualization plays a key role in the greenification of the department.
The addition of virtual machines onto a single physical server typically represents a trivial, if even measurable, increase in power draw. Adding additional physical servers, of course, adds a significant amount of power consumption even for systems that are lightly used or used only occasionally.
Reducing backup complexity: Virtualized servers can be backed up using completely traditional methods such as file system level backups from the operating system itself as made popular by traditional backup systems like NetBackup, BackupExec, Amanda, Bacula and others.
So if we desire to stick with current backup strategies we can without any additional complexity, but if we want to move to image-based backups we can do so quite easily. Using system images as backups is not necessarily new or unique to virtualization but virtualization makes this far more obvious and accessible for many users.
In fact, with virtualization system images (a copy of the entire system, not just of its individual files) can be taken using nothing but the regular filesystem - no special software needed. A complete system backup can be taken by simply shutting down the virtual server, making a copy of its virtual filesystem - often a single, large file, and starting the system up again.
Restoring a system can be a simple as copying an image file from a backup storage device to the virtual server and starting it back up. Restore done. System back online.
This is as simple as it gets.
Ease of provisioning: Building a new server operating system directly on hardware is a time consuming venture for most shops.
This is especially true if there are any surprises with new hardware type that has not been used previously. There may be missing drivers or special operating system settings and parameters needed to support the hardware. With virtualization the target platform is always identical, removing many surprises from this process. This make it both faster and more reliable.
In many cases deployment is also faster simply because the process of preparing the base machine is so much faster. To kick off a manual install of Linux on a traditional physical server I must purchase the server, install into rack, connect power and networking, provision networking, turn on server, update firmware, configure out of band management system, burn in hardware, install installation media and begin installing.
Or from some virtualization environments I can simply kick off the entire process with a single command at the command line. Deploying a new server could go from hours or days to minutes. This does not even begin to address the simplicity of cloning existing systems within a virtual environment.
Significant software cost savings: Some vendors, like Novell with Suse Linux, allow you to virtualize as many servers as you want on a single physical machine while paying for only a single machine license. Red Hat gives you multiple installs but not unlimited like Novell. Microsoft has a range of virtualization pricing options depending on your needs, including an unlimited per processor deployment license.
In a worst case scenario you will need to pay for additional operating system and other software licenses exactly as if you were running the same machines physically but in almost all cases there is more pricing flexibility and often dramatic cost reductions for multiple virtualized hosts.
The ability to "roll back" an entire operating system: Most virtualization platforms allow for a concept of taking a system snapshot, making changes to the active system and then restoring the system back to its original state when done. This is great for software testing. Its especially good for testing operating system patches or any critical update process where, if something went wrong, it could cause your system to become unresponsive and potentially not repairable.
The ability to go "back in time" to the latest snapshot, taken seconds before the patch application or risky configuration change can be a lifesaver. Of course taking an image backup could be used in the same way but snapshots allow for even more rapid recovery due to their "proximity" to the original file system.
All the benefits mentioned above come with a move to virtualization and do not require additional cost for software or hardware.
If our budget allows and the need exists there is also the option of adding one of more virtualization servers and having these servers share a SAN for storage of virtual machine images. At a minimum this will roughly triple the hardware cost but provides double the processing power and some really amazing features.