Daniel Verkamp 4609215690 doc/nvmf: clean up and reorder the nvmf_tgt docs

- Remove outdated section about pre-release kernels; the Linux kernel
  support has been in released kernels for a while now.
- Switch to ./configure rather than `make CONFIG_...`.
- Put the target configuration into subsections, and move it earlier in
  the doc.
- Clean up some wording and style issues.

Change-Id: I86e79226a73c4e36ed8a440294957ea824f24f0b
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-on: https://review.gerrithub.io/395869
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

2018-01-24 15:40:04 -05:00

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NVMe over Fabrics Target

@sa @ref nvme_fabrics_host

NVMe-oF Target Getting Started Guide

The NVMe over Fabrics target is a user space application that presents block devices over the network using RDMA. It requires an RDMA-capable NIC with its corresponding OFED software package installed to run. The target should work on all flavors of RDMA, but it is currently tested against Mellanox NICs (RoCEv2) and Chelsio NICs (iWARP).

The NVMe over Fabrics specification defines subsystems that can be exported over the network. SPDK has chosen to call the software that exports these subsystems a "target", which is the term used for iSCSI. The specification refers to the "client" that connects to the target as a "host". Many people will also refer to the host as an "initiator", which is the equivalent thing in iSCSI parlance. SPDK will try to stick to the terms "target" and "host" to match the specification.

The Linux kernel also implements an NVMe-oF target and host, and SPDK is tested for interoperability with the Linux kernel implementations.

If you want to kill the application using signal, make sure use the SIGTERM, then the application will release all the share memory resource before exit, the SIGKILL will make the share memory resource have no chance to be released by application, you may need to release the resource manually.

Prerequisites

This guide starts by assuming that you can already build the standard SPDK distribution on your platform. By default, the NVMe over Fabrics target is not built. To build nvmf_tgt there are some additional dependencies.

Fedora:

dnf install libibverbs-devel librdmacm-devel

Ubuntu:

apt-get install libibverbs-dev librdmacm-dev

Then build SPDK with RDMA enabled:

./configure --with-rdma <other config parameters>
make

Once built, the binary will be in app/nvmf_tgt.

Prerequisites for InfiniBand/RDMA Verbs

Before starting our NVMe-oF target we must load the InfiniBand and RDMA modules that allow userspace processes to use InfiniBand/RDMA verbs directly.

modprobe ib_cm
modprobe ib_core
modprobe ib_ucm
modprobe ib_umad
modprobe ib_uverbs
modprobe iw_cm
modprobe rdma_cm
modprobe rdma_ucm

Prerequisites for RDMA NICs

Before starting our NVMe-oF target we must detect RDMA NICs and assign them IP addresses.

Mellanox ConnectX-3 RDMA NICs

modprobe mlx4_core
modprobe mlx4_ib
modprobe mlx4_en

Mellanox ConnectX-4 RDMA NICs

modprobe mlx5_core
modprobe mlx5_ib

Assigning IP addresses to RDMA NICs

ifconfig eth1 192.168.100.8 netmask 255.255.255.0 up
ifconfig eth2 192.168.100.9 netmask 255.255.255.0 up

Configuring the SPDK NVMe over Fabrics Target

A nvmf_tgt-specific configuration file is used to configure the NVMe over Fabrics target. This file's primary purpose is to define subsystems. A fully documented example configuration file is located at etc/spdk/nvmf.conf.in.

You should make a copy of the example configuration file, modify it to suit your environment, and then run the nvmf_tgt application and pass it the configuration file using the -c option. Right now, the target requires elevated privileges (root) to run.

app/nvmf_tgt/nvmf_tgt -c /path/to/nvmf.conf

Subsystem Configuration

The [Subsystem] section in the configuration file is used to configure subysystems for the NVMe-oF target.

This example shows two local PCIe NVMe devices exposed as separate NVMe-oF target subsystems:

[Nvme]
TransportID "trtype:PCIe traddr:0000:02:00.0" Nvme0
TransportID "trtype:PCIe traddr:0000:82:00.0" Nvme1

[Subsystem1]
NQN nqn.2016-06.io.spdk:cnode1
Listen RDMA 192.168.100.8:4420
AllowAnyHost No
Host nqn.2016-06.io.spdk:init
SN SPDK00000000000001
Namespace Nvme0n1 1

[Subsystem2]
NQN nqn.2016-06.io.spdk:cnode2
Listen RDMA 192.168.100.9:4420
AllowAnyHost Yes
SN SPDK00000000000002
Namespace Nvme1n1 1

Any bdev may be presented as a namespace. See @ref bdev for details on setting up bdevs. For example, to create a virtual controller with two namespaces backed by the malloc bdevs named Malloc0 and Malloc1 and made available as NSID 1 and 2:

[Subsystem3]
  NQN nqn.2016-06.io.spdk:cnode3
  Listen RDMA 192.168.2.21:4420
  AllowAnyHost Yes
  SN SPDK00000000000003
  Namespace Malloc0 1
  Namespace Malloc1 2

Assigning CPU Cores to the NVMe over Fabrics Target

SPDK uses the DPDK Environment Abstraction Layer to gain access to hardware resources such as huge memory pages and CPU core(s). DPDK EAL provides functions to assign threads to specific cores. To ensure the SPDK NVMe-oF target has the best performance, configure the RNICs and NVMe devices to be located on the same NUMA node.

The -m core mask option specifies a bit mask of the CPU cores that SPDK is allowed to execute work items on. For example, to allow SPDK to use cores 24, 25, 26 and 27:

app/nvmf_tgt/nvmf_tgt -m 0xF000000

Configuring the Linux NVMe over Fabrics Host

Both the Linux kernel and SPDK implement an NVMe over Fabrics host. The Linux kernel NVMe-oF RDMA host support is provided by the nvme-rdma driver.

modprobe nvme-rdma

The nvme-cli tool may be used to interface with the Linux kernel NVMe over Fabrics host.

Discovery:

nvme discover -t rdma -a 192.168.100.8 -s 4420

Connect:

nvme connect -t rdma -n "nqn.2016-06.io.spdk:cnode1" -a 192.168.100.8 -s 4420

Disconnect:

nvme disconnect -n "nqn.2016-06.io.spdk:cnode1"

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