Patent ID: 7284104

Claim:
A method for backing up one or more files including a first file, comprising: generating a first snappoint of a volume, wherein the first snappoint is a dataful snappoint in that it includes information indicative of the contents of said volume at a first point in time and information indicating which portions of said volume have been modified subsequent to said first point in time and prior to a second point in time corresponding to a second snappoint; using said first snappoint to perform a backup of said volume to a backup device; subsequent to said first point in time, updating said first snappoint; generating said second snappoint of said volume at said second point in time; performing an incremental backup of said first file after said second point in time by: accessing information mapping said first file to said volume; using said information mapping said first file to said volume to determine whether said first snappoint indicates that any portions of said volume that map to said first file have been modified; if said first snappoint indicates that any portions of said volume that map to said first file have been modified, copying the modified portions from said second snappoint to said backup device, and not copying portions of said volume that map to said first file that have not been modified; and in response to completion of said copying from said second snappoint, changing the first snappoint from a dataful snappoint into a dataless snappoint, wherein said dataless snappoint identifies which portions of the volume are modified relative to said first point in time without identifying the actual contents of the modified portions.