“Files are not stored redundantly but are kept on removable storage media which can be carried around during prolonged partitions. Thus availability & consistency are simultaneously achieved” Disk Toting
Origin Points • System wide unique identifier generated when the file is created • Immutable attribute of the file • Suggested: Creation Time & Creation Site Pair • Detect Name Conflicts
“Each partition can break into sub partitions and/or merge with other partitions many times before the entire network finally becomes connected” The Partition Problem
Version Vectors “A Version Vector for a file f is a sequence of n pairs, where n is the number of sites at which f is stored … the ith vector entry counts the number Vi of updates to f made at site Si”
Version Vectors • For each update of f on site Si we increment the Sith component of the version vector • When conflicts are reconciled the Max Sith entry is set in the version vector • Version vectors encode the partial order defined by the partition graph
Conflict Resolution “A conflict detection mechanism, while valuable, has increased effect if there is also a method for reconciling conflicts automatically”
Conflict Resolution “Clearly, conflict reconciliation must take into account the semantics of the operations which were done to the data object in conflict”