Concurrency control is essential in multiuser storage systems. In this thesis, we design and implement the concurrency control manager of the KAist Object Storage System(KAOSS), a general-purpose object storage system. The concurrency control manager employs the strict two-phase locking protocol for ensuring serializability. Our concurrency control manager (1) supports multiple granularity locking with page and file levels, (2) provides an efficient concurrency control mechanism for the KAOSS $B^+$tree, a $B^+$tree variant, which allows variable length keys and duplicated keys, (3) solves the phantom problem using key-range locking, and (4) handles deadlocks based on the wait-for graph.
