Many of you realize that I am pretty close to the Citrix Project Kensho OVF Tool.Frankly, I find it as a very useful tool with some very useful features.
First of all – let me mention a bit about OVF again. OVF is NOT a method of converting virtual machines. OVF is a way to describe a virtual appliance using standardized XML tags, so that various platforms can consume and use that virtual appliance as it was defined.
A virtual appliance has traditionally been though of as a single virtual machine (thank you VMware). However, a virtual appliance is actually a “workload.”
Many of you might realize that an enterprise application is rarely a simple single .exe file that simply runs on a desktop. A very simple reporting application might be an executable, a SQL database, and even a document archiving system. All of these entities grouped together is the workload.
It takes all of these pieces working together for the application to be fully functional and feature rich. The Application Workload would be a better way to describe this.
In the same light there is a component that might participate in multiple workloads – the SQL server can serve databases to multiple front-end and back-end applications. It would have the most complex relationship in this example.
This brings me pack to the virtual appliance – the OVF is a description of the workload. This example has that defined as two servers and one client.
If you are the person creating the package, you might leave the client out of the package, or only deliver the client executable as a component of the package, but it is not imported to a virtualization host as a virtual machine.
Some might call this creative thinking, but really it is just taking what the OVF allows and applying that to real situations.
The OVF standard (VMAN at the DMTF) is still evolving and changing. And vendors are still working on compatibility and pushing those standards to ever complex designs.It is because of this that not all vendors support each other. They have to choose to allow for consumption of other implementations of the OVF standard. Yes, this gets very complex and interwoven and creates a bummer for some folks that see OVF as the answer to virtual machine portability – when that portability has far more to do with the applications and operating systems within the virtual appliance themselves than it does in the depths of an XML file.