Performing block based striped backups in a storage system, by: obtaining a used block bitmap for a source volume to be backed up, defining a number of parallel save streams to simultaneously transmit separate data streams from the source volume to backup media of the storage system, converting the used block bitmap to the respective data streams based on the number of defined parallel save streams, embedding each data stream in a differencing disk payload, and maintaining a differencing disk chain across all data streams to create a last differencing disk that refers to all preceding differencing disks. The storage system may include AFTD devices in which the method mounts the last differencing disk to present a complete saveset, or data domain devices in which case the method synthesizes the respective data streams after a backup operation to present a complete saveset.