applications l Interacts with MDS to add, delete, modify, and query metadata l Interacts with the chunkServer to read and write data 4. Snapshotcloneserver l Independent of core services l Snapshot data configured 3. Each file (/foo/bar) contains chunks scattered all over the storage nodes. ChunkServer provides 4KB random read/write capability to support 4KB aligned read/write on block devices mainly describes how data nodes manage chunk. Each node in the figure represents a data node (ChunkServer). A CopySet is the basic unit of data replication in CurveBS. A CopySet contains multiple chunks