US Patent 9454536 Space compaction and defragmentation mechanisms in data space

Moving previous version data required to be restored beyond a continuous data protection window, if required, to facilitate efficient reclamation and reallocation of storage allocated to a continuous data protection journaling process is disclosed. In some embodiments, storage is allocated when possible in an allocation group that enables a continuous data protection or other backup process to perform a series of successive write operations without requiring that a write head be moved inefficiently to many arbitrary points on the storage media.