"Space Doctor permits users to update to the new Apple HFS+ format without the need to reformat existing hard drives. Apple's HFS+ makes more efficient use of disk space by reducing the minimum file size. Space Doctor has been tested in real world conditions and has been as much as 20 times faster than competing products. Space Doctor is also extremely safe and is impervious to data loss in the event of a power outage, even during the update process. It also offers users the option to cancel the process with complete safety at any time prior to completion of the update.
Prior to performing the update, Space Doctor will calculate the savings that will result and advises the user as to how much additional space will be gained."