File system backups are performed by copying information describing changes in the file system since a previous point in time. To restore data, a virtual restored file system (VRFS) structure is created corresponding to a snapshot of data copied from the file system that is stored in the backup file system. A client can read the data stored in the backup file system pointed at by the VRFS structure as well as write to the backup file system. Multiple clients can share blocks of data stored on the backup file system via the same VRFS structure or via multiple VRFS structures. If a client writes to a data block pointed at by a VRFS, a copy of the data block is made to which the client makes changes so that the data in the original data blocks is saved for other clients.