A software appliance is a

software application Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

combined with just enough operating system (JeOS) to run optimally on industry-standard hardware (typically a

server Server may refer to: Computing *Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients Role * Waiting staff, those who work at a restaurant or a bar attending customers and su ...

) or in a

virtual machine In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized h ...

. It is a software distribution or

firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...

that implements a

computer appliance A computer appliance is a home appliance with software or firmware that is specifically designed to provide a specific computing resource. Such devices became known as ''appliances'' because of the similarity in role or management to a home ap ...

Virtual appliance A virtual appliance is a pre-configured virtual machine image, ready to run on a hypervisor; virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine and packaging that ...

s are a subset of software appliances. The main distinction is the packaging format and the specificity of the target platform. A virtual appliance is a

virtual machine image A disk image, in computing, is a computer file containing the contents and structure of a disk volume or of an entire data storage device, such as a hard disk drive, tape drive, floppy disk, optical disc, or USB flash drive. A disk image is usua ...

designed to run on a specific virtualization platform, while a software appliance is often packaged in more generally applicable image format (e.g.,

Live CD A live CD (also live DVD, live disc, or live operating system) is a complete bootable computer installation including operating system which runs directly from a CD-ROM or similar storage device into a computer's memory, rather than loading f ...

) that supports installations to physical machines and multiple types of virtual machines.Wu C F, Wang Y S, Liu G N, Amies, A, 2012
Create solutions on IBM SmartCloud Enterprise: Transfer image assets between different accounts
''IBM developerWorks'', June 6. Installing a software appliance to a virtual machine and packaging that into an image, creates a virtual appliance.

Benefits

Software appliances have several benefits over traditional software applications that are installed on top of an

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

: * Simplified deployment: A software appliance encapsulates an application's dependencies in a pre-integrated, self-contained unit. This can dramatically simplify software deployment by freeing users from having to worry about resolving potentially complex OS compatibility issues, library dependencies or undesirable interactions with other applications. This is known as a "

toaster A toaster is a small electric appliance that uses radiant heat to brown sliced bread into toast. Types Pop-up toaster In pop-up or automatic toasters, a single vertical piece of bread is dropped into a slot on the top of the toaste ...

." * Improved isolation: software appliances are typically used to run applications in isolation from one another. If the security of an appliance is compromised, or if the appliance crashes, other isolated appliances will not be affected. * Improved performance: A software appliance does not embed any unused operating system services, applications or any form of

bloatware Software bloat is a process whereby successive versions of a computer program become perceptibly slower, use more memory, disk space or processing power, or have higher hardware requirements than the previous version, while making only dubious us ...

hence it does not have to share the hardware resources (CPU, memory, storage space, ...) usually consumed by these on a generic OS setup. This naturally leads to faster boot time and application execution speed. In the case where multiple software appliances share and run simultaneously on the same hardware (on a virtualization platform for example) this will not hold true as running n instances of a software appliance (OS + software application) will consume more hardware resources than running n instances of a software application on 1 instance of an operating system due to the overhead of running n - 1 more instances of operating system.

Types of software appliances

Virtual appliance

A software appliance can be packaged in a

format as a

virtual appliance A virtual appliance is a pre-configured virtual machine image, ready to run on a hypervisor; virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine and packaging that ...

, allowing it to be run within a virtual machine container. A virtual appliance could be built using either a standard virtual machine format such as Open Virtualization Format (OVF), or a format specific to a particular virtual machine container (for example, VMware, VirtualBox, or Amazon EC2).

Containers

Containers A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping. Things kept inside of a container are protected on several sides by being inside of its structure. The term ...

and their images (such as those provided by Docker and Docker Hub) can be seen as an implementation of software appliances.

Live CD appliance

A software appliance can be packaged as a

image, allowing it to run on real hardware in addition to most types of virtual machines. This allows developers to avoid the complexities involved in supporting multiple incompatible virtual machine image formats and focus on the lowest common denominator instead (i.e., ISO images are supported by most Virtual Machine platforms).

Commercial software appliances

Commercial software appliances are typically sold as a subscription service (pay-as-you-go) and are an alternative approach to

software as a service Software as a service (SaaS ) is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. SaaS is also known as "on-demand software" and Web-based/Web-hosted software. SaaS is con ...

. Customers can receive all service and maintenance from the application vendor, eliminating the requirement to manage multiple maintenance streams, licenses, and service contracts. In some cases, the application vendor may install the software appliance on a piece of hardware prior to delivery to the customer, thereby creating a

. In both cases, the primary value to the customer remains the simplicity of purchase, deployment, and maintenance.

References

{{DEFAULTSORT:Appliance, software Software distribution Operating system distributions bootable from read-only media