A ghosting filter on a computing device perceives that a file is in a
ghosted form and commands a file system of the device to retrieve
ghosting information from the ghosted file. The ghosting filter receives
a read command from an application on the device with respect to a
portion of the data of the ghosted file. The read command has parameters
including an offset into the portion of the data and a read length with
respect to such portion. The ghosting filter initiates reconstituting of
the portion of the data of the ghosted file based on the received
ghosting information and data of the ghosted file at an alternate
location, and after the portion of the data of the ghosted file has been
reconstituted responds to the read command with the portion of the data
requested.