Javadoc
OVF allows a disk image to be represented as a set of modified blocks in comparison to a
parent image. The use of parent disks can often significantly reduce the size of an OVF
package, if it contains multiple disks with similar content. For a Disk element, a parent disk
may optionally be specified using the
parentRef attribute, which shall contain a valid
ovf:id reference to a different Disk element. If a disk block does not exist locally, lookup
for that disk block then occurs in the parent disk. In
DiskSection, parent Disk
elements shall occur before child Disk elements that refer to them.