During a roundtable discussion held recently, assertions were made by various participants that there's a central standard for virtualisation, called OVF/OVA. Subsequent research unearthed an interesting blog post by Damian Karlson, a cloud solutions architect at ServiceMesh in the US.
OVF is a packaging standard designed to address the portability and deployment of virtualisation appliances.
He writes: "Chances are good that you've run into an OVF/OVA from a variety of sources: as a packaged application or appliance from a vendor, as a download from the VMware community appliances site, or even while physically moving virtual machine files from one location to another.
"An OVF refers to the Open Virtualisation Format, which is a 'packaging standard designed to address the portability and deployment of virtualisation appliances'. The OVF format standard was formed by the Distributed Management Task Force, or DMTF, which is an industry working group comprised of over 160 member companies and organisations.
"An OVF package structure consists of a number of files: a descriptor file, optional manifest and certificate files, optional disk images, and optional resource files (such as ISOs). The optional disk image files can be VMware VMDKs, or any other supported disk image file."
Karlson links to a definition posted on the DMTF Web site: "DMTF's Open Virtualisation Format (OVF) is a packaging standard designed to address the portability and deployment of virtual appliances. OVF enables simplified and error-free deployment of virtual appliances across multiple virtualisation platforms.
"OVF is a common packaging format for independent software vendors (ISVs) to package and securely distribute virtual appliances, enabling cross-platform portability. By packaging virtual appliances in OVF, ISVs can create a single, pre-packaged appliance that can run on customers' virtualisation platforms of choice."
According to Karlson, OVF is not only the name of the packaging format standard, but also refers to the package when distributed as a group of files. An OVA (open virtual appliance or application) is merely a single file distribution of the same file package, stored in the TAR format.
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