A method, apparatus, and article of manufacture for performing a point-in-time backup using a snapshot function. Work space on a work virtual volume is obtained to hold the snapshot copy of the source data being copied from a source virtual volume. Updates to the source virtual volume are suspended during the snapshot function, so as to provide a logically consistent view of the source virtual volume at a common point in time. Pointers are copied from a virtual track table of the source virtual volume to a virtual track table of the work virtual volume without actually moving any data on data storage devices referenced by those pointers. As a result, the snapshot function provides a method for copying the source virtual volume to the work virtual volume very quickly. Upon completion of the snapshot function, updates to the source virtual volume may be resumed. Subsequently, a backup is performed in the usual manner, except that the backup retrieves the source data from the work virtual volume rather than the source virtual volume.