A virtual appliance is a minimalist virtual machine image designed to run under any virtualization technology.
A key concept that differentiates a virtual appliance from a virtual machine is that a virtual appliance is a fully pre-installed and pre-configured application and operating system environment whereas a virtual machine is, by itself, without application software.
Typically a virtual appliance will have a web interface to configure the inner workings of the appliance. A virtual appliance is usually built to host a single application, and so represents a new way of deploying network applications.
As an example, the MediaWiki software that powers Wikipedia is available as a virtual appliance. This appliance contains all the necessary software, including operating system, database and MediaWiki, to run a wiki installation as a “black box”.
Benefits of Deploying Virtual Appliances?
Since software applications are pre-installed and pre-configured with an operating system and packaged in a run-to-ready format, virtual appliances eliminate complex, expensive, and lengthy, error prone installation and configuration cycles.
Virtual appliances running on JeOS (pronounced “Juice”) – Just enough Operating System – are less vulnerable to security breaches. A JeOS is a stripped down version designed to support the specific workload it runs. Since JeOS only includes the programs and components required to successfully support the specific application, it occupies a much smaller footprint compared to general purpose operating systems and therefore fewer attack vectors are exposed. JeOS is also much easier to maintain and manage since fewer updates are required for a slimmer OS.
Easier IT management:
Customers need not worry about their dependence on 3rd party tools for IT management. By deploying virtual appliances on VI, customers can instantly leverage key capabilities such as
Portability and Vendor Independence:
Virtual appliances deliver the greatest level of flexibility for customers.