Presented herein are mass data storage systems, file system protocols, non-transitory machine readable devices, and methods for storing data blocks in data file systems. Methods for compressing snapshot data in a data file system are disclosed which include: loading a snapshot file with one or more data blocks, the snapshot representing a state of the data file system at a point in time; determining if at least one of the snapshot data blocks is less than a predetermined byte value; responsive to a snapshot data block having a size that is less than the predetermined byte value, identifying a packed block configured to store data chunks from plural distinct snapshots and having available sufficient storage space to store the snapshot data block; and adding to the packed block the snapshot data block and lost-write context information corresponding to the snapshot data block.