Virtual Appliances are portable virtual machines. One can export a virtual machine as a virtual appliance, and then you can also import the virtual appliance back as a virtual machine.
Virtual Appliances are available either as a folder of files – OVF (Open Virtualization format) or as a single (tarball) file – OVA (Open Virtualization archive).
Why use Virtual Appliances?
Since you already have a existing virtual Infrastructure, you can use the same for running virtual appliances. Virtual Appliances are essentially a VM which is pre-installed with a Operating System (OS) and an application. Virtual Appliances are built is such a way that you just import the appliance and start using it with a minimal network and application configuration.
Advantages of Virtual Appliances:
Both physical and virtual will require a approval from the finance team. However after the finance approval, implementing a virtual appliance will require no more approvals.
- No need for approval from the data-center team for rack space
- No need for approval from the networking team for free ports on network switches
- No need for approval for power requirement
- No need for approval for air conditioning or cooling needs
All these approvals basically increase your deployment time to anything about 4-6 weeks, whereas if using a virtual appliance that comes down to about 2 hours. Other advantages of virtual appliances include:
- Standard off-the-shelf server hardware used for running virtual appliances
- Reduces AMC costs as one less hardware vendor to manage
- Easy to standardize on a single hardware vendor
- Improves return on your investment in hardware infrastructure
You can find several free and paid appliances available from various vendors. VMware has something called as VMware Virtual Appliance Marketplace. Several free Linux based opensource virtual appliances are available from Turnkey Linux. You can also build your own virtual appliances using the SUSE Studio. You can also find a free Linux based L3 switch appliance at VyOS. You can also find the excellent Monowall Firewall as a virtual appliance for vSphere.
Overall I believe virtual appliances are here to stay and the easy of management and deployment is what makes them a very attractive form factor.