Virtual appliances are quickly becoming an integral part of the virtual infrastructure. One of our experts even called virtual appliances the “new frontier
of application delivery.” That’s because a virtual appliance takes simple application deployment and makes it even simpler.
A virtual appliance is basically a virtual machine (VM) image file containing a preconfigured operating system environment, a single application and a virtual disk file. Simply put, a virtual appliance is a pre-built VM -- with only the absolutely necessary components.
The answers to these frequently asked questions about virtual appliances will help you understand the benefits of virtual appliances, how to deploy an appliance and some of the drawbacks, including difficulty troubleshooting and inflexibility. We also take you through creating a virtual appliance with Ubuntu and using VMsafe-aware virtual appliances.
What are the benefits of virtual appliances?
Software deployment usually requires several manual processes, but using virtual appliances significantly decreases deployment time. It also guarantees full support from the provider and easy transport if you need to move the virtual appliance among servers. It’s easier to upgrade resources for virtual appliances because you can just stop the VM to add RAM or disks, for example, and restart it. Backup is also easier, through virtual machine snapshots. But make sure the virtual appliance relies on the same virtualization technology you’ve deployed, or you might have to convert the appliance into a new format for integration.
What are the drawbacks of deploying a virtual appliance?
When you deploy a virtual appliance, a new VM is created using the hardware configuration specified in the appliance’s Open Virtualization Format (OVF) file. The disks on a virtual appliance are usually shrunk for packaging, and unused disk blocks are removed. But once the VM is unpackaged, virtual disks are copied to the host and increased to the size indicated in the file. The virtual disks are then attached to the VM, and the machine can power on.
Understanding the OVF format helps illuminate the benefits of virtual appliances, but you should also know some drawbacks. It’s not easy to customize the operating system and applications, because a virtual appliance is preconfigured. That also makes troubleshooting more difficult. Finally, patch management is trickier because you can’t use traditional patch methods or your own patching schedule.
How will VMsafe virtual appliances affect my infrastructure?
VMsafe is an application programming interface that protects applications running in VMs. Many VMsafe-aware applications come as virtual appliances, but the implementation process is complicated. What makes a VMsafe-aware virtual appliance unique is that it has access to the data structures within the hypervisor, including all reads and writes to memory, storage or the network. But that also means that security is a top concern. VMware vSphere does not guarantee protection of these virtual appliances, so it’s your responsibility to place it behind a firewall within its own security zone.
How can I create a virtual appliance with Ubuntu?
Ubuntu offers a version specifically designed to create virtual appliances -- called Ubuntu JeOS, which stands for “just enough operating system.” Its kernel is stripped down to include only those components a virtual appliance needs, so JeOS runs more efficiently than other Ubuntu Server editions. It provides a simple operating system on which to deploy the preconfigured application. Installation and implementation are straightforward, and then the fun begins. With JeOS, individual users can configure the virtual appliance to fit their needs.
How has the virtual appliance market evolved?
A history of virtual appliances is helpful to know when you’re diving into this technology. You probably didn’t know that BEA Systems (acquired by Oracle in 2008) developed some of the earliest virtual appliances. Today, VMware offers many of its management tools as virtual appliances, and VMTurbo is also making headway in the virtual appliance marketplace. But the details of what makes up a virtual appliance -- and what exactly the mini-VM does -- are what will really help you get started.
This was first published in February 2011