Cloud space reclamation
MSDP stores data segments in data containers, and data containers are sent to cloud storage and stored as objects. The segments in one container may belong to the different backup images. When backup images expire, their segments become garbage. If all segments in one container are garbage, the whole container can be reclaimed. If not, that container cannot be reclaimed because it contains both useful data and garbage. A small number of segments in one container may prevent that container from being reclaimed for a long time if those segments are referenced by many backup images.
MSDP uses container aging and cloud compaction to reclaim the space in these containers.