In a specific embodiment, the present invention provides a method of providing transparent file backup service based on networked computers. The method includes establishing an online redundant array of independent disks (RAID) of a plurality of networked computers maintained by a central service controller on a server. The plurality of networked computers belong to one or more subscribed users. The method further includes storing backup files of each subscribed user on the online RAID. Each subscribed user dedicating at least a portion of storage spaces on corresponding computers to the online RAID for backup files of one or more alternative subscribed users. The central service controller in conjunction of a client software running on each user's computer is configured to coordinate backup file distribution and restoration.