1# NVMe over Fabrics Target {#nvmf} 2 3@sa @ref nvme_fabrics_host 4@sa @ref nvmf_tgt_tracepoints 5 6# NVMe-oF Target Getting Started Guide {#nvmf_getting_started} 7 8The SPDK NVMe over Fabrics target is a user space application that presents block devices over a fabrics 9such as Ethernet, Infiniband or Fibre Channel. SPDK currently supports RDMA and TCP transports. 10 11The NVMe over Fabrics specification defines subsystems that can be exported over different transports. 12SPDK has chosen to call the software that exports these subsystems a "target", which is the term used 13for iSCSI. The specification refers to the "client" that connects to the target as a "host". Many 14people will also refer to the host as an "initiator", which is the equivalent thing in iSCSI 15parlance. SPDK will try to stick to the terms "target" and "host" to match the specification. 16 17The Linux kernel also implements an NVMe-oF target and host, and SPDK is tested for 18interoperability with the Linux kernel implementations. 19 20If you want to kill the application using signal, make sure use the SIGTERM, then the application 21will release all the share memory resource before exit, the SIGKILL will make the share memory 22resource have no chance to be released by application, you may need to release the resource manually. 23 24## RDMA transport support {#nvmf_rdma_transport} 25 26It requires an RDMA-capable NIC with its corresponding OFED (OpenFabrics Enterprise Distribution) 27software package installed to run. Maybe OS distributions provide packages, but OFED is also 28available [here](https://downloads.openfabrics.org/OFED/). 29 30### Prerequisites {#nvmf_prereqs} 31 32To build nvmf_tgt with the RDMA transport, there are some additional dependencies. 33 34Fedora: 35~~~{.sh} 36dnf install libibverbs-devel librdmacm-devel 37~~~ 38 39Ubuntu: 40~~~{.sh} 41apt-get install libibverbs-dev librdmacm-dev 42~~~ 43 44Then build SPDK with RDMA enabled: 45 46~~~{.sh} 47./configure --with-rdma <other config parameters> 48make 49~~~ 50 51Once built, the binary will be in `app/nvmf_tgt`. 52 53### Prerequisites for InfiniBand/RDMA Verbs {#nvmf_prereqs_verbs} 54 55Before starting our NVMe-oF target with the RDMA transport we must load the InfiniBand and RDMA modules 56that allow userspace processes to use InfiniBand/RDMA verbs directly. 57 58~~~{.sh} 59modprobe ib_cm 60modprobe ib_core 61# Please note that ib_ucm does not exist in newer versions of the kernel and is not required. 62modprobe ib_ucm || true 63modprobe ib_umad 64modprobe ib_uverbs 65modprobe iw_cm 66modprobe rdma_cm 67modprobe rdma_ucm 68~~~ 69 70### Prerequisites for RDMA NICs {#nvmf_prereqs_rdma_nics} 71 72Before starting our NVMe-oF target we must detect RDMA NICs and assign them IP addresses. 73 74### Finding RDMA NICs and associated network interfaces 75 76~~~{.sh} 77ls /sys/class/infiniband/*/device/net 78~~~ 79 80#### Mellanox ConnectX-3 RDMA NICs 81 82~~~{.sh} 83modprobe mlx4_core 84modprobe mlx4_ib 85modprobe mlx4_en 86~~~ 87 88#### Mellanox ConnectX-4 RDMA NICs 89 90~~~{.sh} 91modprobe mlx5_core 92modprobe mlx5_ib 93~~~ 94 95#### Assigning IP addresses to RDMA NICs 96 97~~~{.sh} 98ifconfig eth1 192.168.100.8 netmask 255.255.255.0 up 99ifconfig eth2 192.168.100.9 netmask 255.255.255.0 up 100~~~ 101 102### RDMA Limitations {#nvmf_rdma_limitations} 103 104As RDMA NICs put a limitation on the number of memory regions registered, the SPDK NVMe-oF 105target application may eventually start failing to allocate more DMA-able memory. This is 106an imperfection of the DPDK dynamic memory management and is most likely to occur with too 107many 2MB hugepages reserved at runtime. One type of memory bottleneck is the number of NIC memory 108regions, e.g., some NICs report as many as 2048 for the maximum number of memory regions. This 109gives us a 4GB memory limit with 2MB hugepages for the total memory regions. It can be overcome by 110using 1GB hugepages or by pre-reserving memory at application startup with `--mem-size` or `-s` 111option. All pre-reserved memory will be registered as a single region, but won't be returned to the 112system until the SPDK application is terminated. 113 114## TCP transport support {#nvmf_tcp_transport} 115 116The transport is built into the nvmf_tgt by default, and it does not need any special libraries. 117 118## Configuring the SPDK NVMe over Fabrics Target {#nvmf_config} 119 120An NVMe over Fabrics target can be configured using JSON RPCs. 121The basic RPCs needed to configure the NVMe-oF subsystem are detailed below. More information about 122working with NVMe over Fabrics specific RPCs can be found on the @ref jsonrpc_components_nvmf_tgt RPC page. 123 124Using .ini style configuration files for configuration of the NVMe-oF target is deprecated and should 125be replaced with JSON based RPCs. .ini style configuration files can be converted to json format by way 126of the new script `scripts/config_converter.py`. 127 128### Using RPCs {#nvmf_config_rpc} 129 130Start the nvmf_tgt application with elevated privileges. Once the target is started, 131the nvmf_create_transport rpc can be used to initialize a given transport. Below is an 132example where the target is started and configured with two different transports. 133The RDMA transport is configured with an I/O unit size of 8192 bytes, 4 max qpairs per controller, 134and an in capsule data size of 0 bytes. The TCP transport is configured with an I/O unit size of 13516384 bytes, 8 max qpairs per controller, and an in capsule data size of 8192 bytes. 136 137~~~{.sh} 138app/nvmf_tgt/nvmf_tgt 139scripts/rpc.py nvmf_create_transport -t RDMA -u 8192 -p 4 -c 0 140scripts/rpc.py nvmf_create_transport -t TCP -u 16384 -p 8 -c 8192 141~~~ 142 143Below is an example of creating a malloc bdev and assigning it to a subsystem. Adjust the bdevs, 144NQN, serial number, and IP address with RDMA transport to your own circumstances. If you replace 145"rdma" with "TCP", then the subsystem will add a listener with TCP transport. 146 147~~~{.sh} 148scripts/rpc.py construct_malloc_bdev -b Malloc0 512 512 149scripts/rpc.py nvmf_subsystem_create nqn.2016-06.io.spdk:cnode1 -a -s SPDK00000000000001 -d SPDK_Controller1 150scripts/rpc.py nvmf_subsystem_add_ns nqn.2016-06.io.spdk:cnode1 Malloc0 151scripts/rpc.py nvmf_subsystem_add_listener nqn.2016-06.io.spdk:cnode1 -t rdma -a 192.168.100.8 -s 4420 152~~~ 153 154### NQN Formal Definition 155 156NVMe qualified names or NQNs are defined in section 7.9 of the 157[NVMe specification](http://nvmexpress.org/wp-content/uploads/NVM_Express_Revision_1.3.pdf). SPDK has attempted to 158formalize that definition using [Extended Backus-Naur form](https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_form). 159SPDK modules use this formal definition (provided below) when validating NQNs. 160 161~~~{.sh} 162 163Basic Types 164year = 4 * digit ; 165month = '01' | '02' | '03' | '04' | '05' | '06' | '07' | '08' | '09' | '10' | '11' | '12' ; 166digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' ; 167hex digit = 'A' | 'B' | 'C' | 'D' | 'E' | 'F' | 'a' | 'b' | 'c' | 'd' | 'e' | 'f' | '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' ; 168 169NQN Definition 170NVMe Qualified Name = ( NVMe-oF Discovery NQN | NVMe UUID NQN | NVMe Domain NQN ), '\0' ; 171NVMe-oF Discovery NQN = "nqn.2014-08.org.nvmexpress.discovery" ; 172NVMe UUID NQN = "nqn.2014-08.org.nvmexpress:uuid:", string UUID ; 173string UUID = 8 * hex digit, '-', 3 * (4 * hex digit, '-'), 12 * hex digit ; 174NVMe Domain NQN = "nqn.", year, '-', month, '.', reverse domain, ':', utf-8 string ; 175 176~~~ 177 178Please note that the following types from the definition above are defined elsewhere: 1791. utf-8 string: Defined in [rfc 3629](https://tools.ietf.org/html/rfc3629). 1802. reverse domain: Equivalent to domain name as defined in [rfc 1034](https://tools.ietf.org/html/rfc1034). 181 182While not stated in the formal definition, SPDK enforces the requirement from the spec that the 183"maximum name is 223 bytes in length". SPDK does not include the null terminating character when 184defining the length of an nqn, and will accept an nqn containing up to 223 valid bytes with an 185additional null terminator. To be precise, SPDK follows the same conventions as the c standard 186library function [strlen()](http://man7.org/linux/man-pages/man3/strlen.3.html). 187 188#### NQN Comparisons 189 190SPDK compares NQNs byte for byte without case matching or unicode normalization. This has specific implications for 191uuid based NQNs. The following pair of NQNs, for example, would not match when compared in the SPDK NVMe-oF Target: 192 193nqn.2014-08.org.nvmexpress:uuid:11111111-aaaa-bbdd-ffee-123456789abc 194nqn.2014-08.org.nvmexpress:uuid:11111111-AAAA-BBDD-FFEE-123456789ABC 195 196In order to ensure the consistency of uuid based NQNs while using SPDK, users should use lowercase when representing 197alphabetic hex digits in their NQNs. 198 199### Assigning CPU Cores to the NVMe over Fabrics Target {#nvmf_config_lcore} 200 201SPDK uses the [DPDK Environment Abstraction Layer](http://dpdk.org/doc/guides/prog_guide/env_abstraction_layer.html) 202to gain access to hardware resources such as huge memory pages and CPU core(s). DPDK EAL provides 203functions to assign threads to specific cores. 204To ensure the SPDK NVMe-oF target has the best performance, configure the NICs and NVMe devices to 205be located on the same NUMA node. 206 207The `-m` core mask option specifies a bit mask of the CPU cores that 208SPDK is allowed to execute work items on. 209For example, to allow SPDK to use cores 24, 25, 26 and 27: 210~~~{.sh} 211app/nvmf_tgt/nvmf_tgt -m 0xF000000 212~~~ 213 214## Configuring the Linux NVMe over Fabrics Host {#nvmf_host} 215 216Both the Linux kernel and SPDK implement an NVMe over Fabrics host. 217The Linux kernel NVMe-oF RDMA host support is provided by the `nvme-rdma` driver 218(to support RDMA transport) and `nvme-tcp` (to support TCP transport). And the 219following shows two different commands for loading the driver. 220 221~~~{.sh} 222modprobe nvme-rdma 223modprobe nvme-tcp 224~~~ 225 226The nvme-cli tool may be used to interface with the Linux kernel NVMe over Fabrics host. 227See below for examples of the discover, connect and disconnect commands. In all three instances, the 228transport can be changed to TCP by interchanging 'rdma' for 'tcp'. 229 230Discovery: 231~~~{.sh} 232nvme discover -t rdma -a 192.168.100.8 -s 4420 233~~~ 234 235Connect: 236~~~{.sh} 237nvme connect -t rdma -n "nqn.2016-06.io.spdk:cnode1" -a 192.168.100.8 -s 4420 238~~~ 239 240Disconnect: 241~~~{.sh} 242nvme disconnect -n "nqn.2016-06.io.spdk:cnode1" 243~~~ 244 245## Enabling NVMe-oF target tracepoints for offline analysis and debug {#nvmf_trace} 246 247SPDK has a tracing framework for capturing low-level event information at runtime. 248@ref nvmf_tgt_tracepoints enable analysis of both performance and application crashes. 249