1******************************** 2RDMA Network Block Device (RNBD) 3******************************** 4 5Introduction 6------------ 7 8RNBD (RDMA Network Block Device) is a pair of kernel modules 9(client and server) that allow for remote access of a block device on 10the server over RTRS protocol using the RDMA (InfiniBand, RoCE, iWARP) 11transport. After being mapped, the remote block devices can be accessed 12on the client side as local block devices. 13 14I/O is transferred between client and server by the RTRS transport 15modules. The administration of RNBD and RTRS modules is done via 16sysfs entries. 17 18Requirements 19------------ 20 21 RTRS kernel modules 22 23Quick Start 24----------- 25 26Server side: 27 # modprobe rnbd_server 28 29Client side: 30 # modprobe rnbd_client 31 # echo "sessname=blya path=ip:10.50.100.66 device_path=/dev/ram0" > \ 32 /sys/devices/virtual/rnbd-client/ctl/map_device 33 34 Where "sessname=" is a session name, a string to identify the session 35 on client and on server sides; "path=" is a destination IP address or 36 a pair of a source and a destination IPs, separated by comma. Multiple 37 "path=" options can be specified in order to use multipath (see RTRS 38 description for details); "device_path=" is the block device to be 39 mapped from the server side. After the session to the server machine is 40 established, the mapped device will appear on the client side under 41 /dev/rnbd<N>. 42 43 44RNBD-Server Module Parameters 45============================= 46 47dev_search_path 48--------------- 49 50When a device is mapped from the client, the server generates the path 51to the block device on the server side by concatenating dev_search_path 52and the "device_path" that was specified in the map_device operation. 53 54The default dev_search_path is: "/". 55 56dev_search_path option can also contain %SESSNAME% in order to provide 57different device namespaces for different sessions. See "device_path" 58option for details. 59 60============================ 61Protocol (rnbd/rnbd-proto.h) 62============================ 63 641. Before mapping first device from a given server, client sends an 65RNBD_MSG_SESS_INFO to the server. Server responds with 66RNBD_MSG_SESS_INFO_RSP. Currently the messages only contain the protocol 67version for backward compatibility. 68 692. Client requests to open a device by sending RNBD_MSG_OPEN message. This 70contains the path to the device and access mode (read-only or writable). 71Server responds to the message with RNBD_MSG_OPEN_RSP. This contains 72a 32 bit device id to be used for IOs and device "geometry" related 73information: side, max_hw_sectors, etc. 74 753. Client attaches RNBD_MSG_IO to each IO message send to a device. This 76message contains device id, provided by server in his rnbd_msg_open_rsp, 77sector to be accessed, read-write flags and bi_size. 78 794. Client closes a device by sending RNBD_MSG_CLOSE which contains only the 80device id provided by the server. 81 82========================================= 83Contributors List(in alphabetical order) 84========================================= 85Danil Kipnis <danil.kipnis@profitbricks.com> 86Fabian Holler <mail@fholler.de> 87Guoqing Jiang <guoqing.jiang@cloud.ionos.com> 88Jack Wang <jinpu.wang@profitbricks.com> 89Kleber Souza <kleber.souza@profitbricks.com> 90Lutz Pogrell <lutz.pogrell@cloud.ionos.com> 91Milind Dumbare <Milind.dumbare@gmail.com> 92Roman Penyaev <roman.penyaev@profitbricks.com> 93