Terms and Symbols ----------------- These are some terms and symbols used in this document. Many are explained in more detail later in the document. Client, Client1, Client2, MDT, OST, MDS, OSS:: The entities exchanging messages. Clients are hosts mounting the Lustre file system. The MDT and OST are services being provided by the Lustre servers MDS and OSS. resource:: A file or directory that is the object of a file system operation, either on the namespace or on its data. RPC request:: RPCs are exchanged in pairs (with a very few exceptions). The request initiates the operation being carried out by the RPC pair. RPC reply:: The matching reply that completes an operation implemented by an RPC pair. MDS_REINT:: An RPC pair that implements an operation that will change the information on an MDT. See <>. LDLM_ENQUEUE:: An RPC pair that implements distributed locking across the servers and clients. See <>. MDS_GETXATTR:: An RPC pair that provides information about extended attributes for a resource. See <>. OST_SETATTR:: An RPC pair that sets resource attributes. See <>. LDLM_BL_CALLBACK:: An RPC pair that assists with getting a lock back from an entity that has it. See <>. LDLM_CP_CALLBACK:: An RPC pair that notifies an entity that a requested lock is now available. See <>. OST_PUNCH:: An RPC pair that modifies the size attribute of a resource on an OST. See <>. 'ptlrpc_body':: The first section (structure) of each RPC. It identifies which RPC operation (opcode) the RPC conveys.