{ OK = 0; // UNKNOWN_ERROR = 1; // NOSPACE = 2; // } // fs interface message GetFsInfoRequest { optional uint32 fsId = 1; // fs id optional string fsName DeleteFsInfoResponse { required MetaStatusCode statusCode = 1; } service MdsService { // fs interface rpc CreateFs(CreateFsRequest) returns (CreateFsResponse); rpc MountFs(MountFsRequest) returns OK = 0; // UNKNOWN_ERROR = 1; // NOSPACE = 2; // } // dentry interface© XXX Page 7 of 15 message GetDentryRequest { required uint32 fsId = 1; required uint64

and NBD use it to access storage services provided by Curve. The client provids posix-like interface, such as read/write/aioread/aiowrite in data plane and open/create/rename/extend, etc in control complete the disk write operation. CurveFS architecture Curvefs implements the file system interface based on FUSE. 1. Fs-meta Cluster is used to manage the inode and dentry metadata of files.

CurveFS can manage different storages (HDFS, OSS, EBS) below • Apps access data by POSIX interface • Infrequent data is moved to OSS, and frequent data is moved to high speed storage transparentlyData

SpaceStatusCode status = 1; // required uint64 chunkId = 2; } service SpaceAllocService { // space interface rpc InitSpace(InitSpaceRequest) returns (InitSpaceResponse); rpc AllocateSpace(AllocateSpaceRequest)