Storage Administration Guide

17.1 Overview #

NVM Express® (NVMe®) is an interface standard for accessing non-volatile storage, commonly SSD disks. NVMe supports much higher speeds and has a lower latency than SATA.

NVMe-oF™ is an architecture to access NVMe storage over different networking fabrics—for example, RDMA, TCP, or NVMe over Fibre Channel (FC-NVMe). The role of NVMe-oF is similar to iSCSI. To increase the fault-tolerance, NVMe-oF has a built-in support for multipathing. The NVMe-oF multipathing is not based on the traditional DM-Multipathing.

The NVMe host is the machine that connects to an NVMe target. The NVMe target is the machine that shares its NVMe block devices.

NVMe is supported on SUSE Linux Enterprise Server 15 SP6. There are Kernel modules available for the NVMe block storage and NVMe-oF target and host.

To see if your hardware requires any special consideration, refer to Section 17.4, “Special hardware configuration”.

17.2 Setting up an NVMe-oF host #

To use NVMe-oF, a target must be available with one of the supported networking methods. Supported are NVMe over Fibre Channel, TCP, and RDMA. The following sections describe how to connect a host to an NVMe target.

17.2.1 Installing command line client #

To use NVMe-oF, you need the nvme command line tool. Install it with zypper:

> sudo zypper in nvme-cli

Use nvme --help to list all available subcommands. Man pages are available for nvme subcommands. Consult them by executing man nvme-SUBCOMMAND. For example, to view the man page for the discover subcommand, execute man nvme-discover.

17.2.2 Discovering NVMe-oF targets #

To list available NVMe subsystems on the NVMe-oF target, you need the discovery controller address and service ID.

> sudo nvme discover -t TRANSPORT -a DISCOVERY_CONTROLLER_ADDRESS -s SERVICE_ID

Replace TRANSPORT with the underlying transport medium: loop, rdma, tcp, or fc. Replace DISCOVERY_CONTROLLER_ADDRESS with the address of the discovery controller. For RDMA and TCP, this should be an IPv4 address. Replace SERVICE_ID with the transport service ID. If the service is IP based, like RDMA or TCP, service ID specifies the port number. For Fibre Channel, the service ID is not required.

The NVMe hosts only see the subsystems they are allowed to connect to.

Example:

> sudo nvme discover -t tcp -a 10.0.0.3 -s 4420

For the FC, the example looks as follows:

> sudo nvme discover --transport=fc \
                --traddr=nn-0x201700a09890f5bf:pn-0x201900a09890f5bf \
                --host-traddr=nn-0x200000109b579ef6:pn-0x100000109b579ef6

For more details, see man nvme-discover.

17.2.3 Connecting to NVMe-oF targets #

After you have identified the NVMe subsystem, you can connect it with the nvme connect command.

> sudo nvme connect -t transport -a DISCOVERY_CONTROLLER_ADDRESS -s SERVICE_ID -n SUBSYSTEM_NQN

Replace TRANSPORT with the underlying transport medium: loop, rdma, tcp or fc. Replace DISCOVERY_CONTROLLER_ADDRESS with the address of the discovery controller. For RDMA and TCP this should be an IPv4 address. Replace SERVICE_ID with the transport service ID. If the service is IP based, like RDMA or TCP, this specifies the port number. Replace SUBSYSTEM_NQN with the NVMe qualified name of the desired subsystem as found by the discovery command. NQN is the abbreviation for NVMe Qualified Name. The NQN must be unique.

Example:

> sudo nvme connect -t tcp -a 10.0.0.3 -s 4420 -n nqn.2014-08.com.example:nvme:nvm-subsystem-sn-d78432

For the FC, the example looks as follows:

> sudo nvme connect --transport=fc \
             --traddr=nn-0x201700a09890f5bf:pn-0x201900a09890f5bf \
             --host-traddr=nn-0x200000109b579ef6:pn-0x100000109b579ef6 \
             --nqn=nqn.2014-08.org.nvmexpress:uuid:1a9e23dd-466e-45ca-9f43-a29aaf47cb21

Alternatively, use nvme connect-all to connect to all discovered namespaces. For advanced usage, see man nvme-connect and man nvme-connect-all.

In case of a path loss, the NVMe subsystem tries to reconnect for a time period, defined by the ctrl-loss-tmo option of the nvme connect command. After this time (default value is 600s), the path is removed and the upper layers of the block layer (file system) are notified. By default, the file system is then mounted read-only, which usually is not the expected behavior. Therefore, it is recommended to set the ctrl-loss-tmo option so that the NVMe subsystem keeps trying to reconnect without a limit. To do so, run the following command:

> sudo nvme connect --ctrl-loss-tmo=-1

To make an NVMe over Fabrics subsystem available at boot, create a /etc/nvme/discovery.conf file on the host with the parameters passed to the discover command (as described in Section 17.2.2, “Discovering NVMe-oF targets”. For example, if you use the discover command as follows:

> sudo nvme discover -t tcp -a 10.0.0.3 -s 4420

Add the parameters of the discover command to the /etc/nvme/discovery.conf file:

echo "-t tcp -a 10.0.0.3 -s 4420" | sudo tee -a /etc/nvme/discovery.conf

Then enable the nvmf-autoconnect service:

> sudo systemctl enable nvmf-autoconnect.service

17.2.4 Multipathing #

NVMe native multipathing is enabled by default. If the CMIC option in the controller identity settings is set, the NVMe stack recognizes an NVME drive as a multipathed device by default.

To manage the multipathing, you can use the following:

Managing multipathing #

nvme list-subsys: Prints the layout of the multipath devices.
multipath -ll: The command has a compatibility mode and displays NVMe multipath devices. Bear in mind that you need to enable the enable_foreign option to use the command. For details, refer to Section 18.13, “Miscellaneous options”.
nvme-core.multipath=N: When the option is added as a boot parameter, the NVMe native multipathing will be disabled.

17.3 Setting up an NVMe-oF target #

17.3.1 Installing command line client #

To configure an NVMe-oF target, you need the nvmetcli command line tool. Install it with zypper:

> sudo zypper in nvmetcli

The current documentation for nvmetcli is available at https://git.infradead.org/users/hch/nvmetcli.git/blob_plain/HEAD:/Documentation/nvmetcli.txt.

17.3.2 Configuration steps #

The following procedure provides an example of how to set up an NVMe-oF target.

The configuration is stored in a tree structure. Use the command cd to navigate. Use ls to list objects. You can create new objects with create.

Start the nvmetcli interactive shell:
```
> sudo nvmetcli
```

Create a new port:

(nvmetcli)> cd ports
(nvmetcli)> create 1
(nvmetcli)> ls 1/
o- 1
  o- referrals
  o- subsystems

Create an NVMe subsystem:

(nvmetcli)> cd /subsystems
(nvmetcli)> create nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82
(nvmetcli)> cd nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82/
(nvmetcli)> ls
o- nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82
  o- allowed_hosts
  o- namespaces

Create a new namespace and set an NVMe device to it:

(nvmetcli)> cd namespaces
(nvmetcli)> create 1
(nvmetcli)> cd 1
(nvmetcli)> set device path=/dev/nvme0n1
Parameter path is now '/dev/nvme0n1'.

Enable the previously created namespace:

(nvmetcli)> cd ..
(nvmetcli)> enable
The Namespace has been enabled.

Display the created namespace:

(nvmetcli)> cd ..
(nvmetcli)> ls
o- nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82
  o- allowed_hosts
  o- namespaces
    o- 1

Allow all hosts to use the subsystem. Only do this in secure environments.

(nvmetcli)> set attr allow_any_host=1
Parameter allow_any_host is now '1'.

Alternatively, you can allow only specific hosts to connect:

(nvmetcli)> cd nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82/allowed_hosts/
(nvmetcli)> create hostnqn

List all created objects:

(nvmetcli)> cd /
(nvmetcli)> ls
o- /
  o- hosts
  o- ports
  | o- 1
  |   o- referrals
  |   o- subsystems
  o- subsystems
    o- nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82
      o- allowed_hosts
      o- namespaces
        o- 1

Make the target available via TCP. Use trtype=rdma for RDMA:

(nvmetcli)> cd ports/1/
(nvmetcli)> set addr adrfam=ipv4 trtype=tcp traddr=10.0.0.3 trsvcid=4420
Parameter trtype is now 'tcp'.
Parameter adrfam is now 'ipv4'.
Parameter trsvcid is now '4420'.
Parameter traddr is now '10.0.0.3'.

Alternatively, you can make it available with Fibre Channel:

(nvmetcli)> cd ports/1/
(nvmetcli)> set addr adrfam=fc trtype=fc traddr=nn-0x1000000044001123:pn-0x2000000055001123 trsvcid=none

Link the subsystem to the port:

(nvmetcli)> cd /ports/1/subsystems
(nvmetcli)> create nqn.2014-08.org.nvmexpress:NVMf:uuid:c36f2c23-354d-416c-95de-f2b8ec353a82

Now you can verify that the port is enabled using dmesg:

# dmesg
        ...
[  257.872084] nvmet_tcp: enabling port 1 (10.0.0.3:4420)

17.3.3 Back up and restore target configuration #

You can save the target configuration in a JSON file with the following commands:

> sudo nvmetcli
(nvmetcli)> saveconfig nvme-target-backup.json

To restore the configuration, use:

(nvmetcli)> restore nvme-target-backup.json

You can also wipe the current configuration:

(nvmetcli)> clear

17.4 Special hardware configuration #

17.4.1 Overview #

Some hardware needs special configuration to work correctly. Skim the titles of the following sections to see if you are using any of the mentioned devices or vendors.

17.4.2 Broadcom #

If you are using the Broadcom Emulex LightPulse Fibre Channel SCSI driver, add a Kernel configuration parameter on the target and host for the lpfc module:

> sudo echo "options lpfc lpfc_enable_fc4_type=3" > /etc/modprobe.d/lpfc.conf

Make sure that the Broadcom adapter firmware has at least version 11.4.204.33. Also make sure that you have the current versions of nvme-cli, nvmetcli and the Kernel installed.

To enable a Fibre Channel port as an NVMe target, an additional module parameter needs to be configured: lpfc_enable_nvmet= COMMA_SEPARATED_WWPNS. Enter the WWPN with a leading 0x, for example lpfc_enable_nvmet=0x2000000055001122,0x2000000055003344. Only listed WWPNs will be configured for target mode. A Fibre Channel port can either be configured as target or as initiator.

17.4.3 Marvell #

FC-NVMe is supported on QLE269x and QLE27xx adapters. FC-NVMe support is enabled by default in the Marvell® QLogic® QLA2xxx Fibre Channel driver.

To confirm NVMe is enabled, run the following command:

> cat /sys/module/qla2xxx/parameters/ql2xnvmeenable

A resulting 1 means NVMe is enabled, a 0 indicates it is disabled.

Next, ensure that the Marvell adapter firmware is at least version 8.08.204 by checking the output of the following command:

> cat /sys/class/scsi_host/host0/fw_version

Last, ensure that the latest versions available for SUSE Linux Enterprise Server of nvme-cli, QConvergeConsoleCLI, and the Kernel are installed. You may, for example, run

# zypper lu && zypper pchk

to check for updates and patches.

For more details on installation, please refer to the FC-NVMe sections in the following Marvell user guides:

17.5 Booting from NVMe-oF over TCP #

SLES supports booting from NVMe-oF over TCP according to the NVM Express® Boot Specification 1.0.

The UEFI pre-boot environment can be configured to attempt NVMe-oF over TCP connections to remote storage servers and use these for booting. The pre-boot environment creates an ACPI table—NVMe Boot Firmware Table (NBFT) to store information about the NVMe-oF configuration used for booting. The operating system uses this table at a later boot stage to set up networking and NVMe-oF connections to access the root file system.

17.5.1 System requirements #

To boot the system from NVMe-oF over TCP, the following requirements must be met:

SLES15 SP6 or later.
A SAN storage array supporting NVMe-oF over TCP
A host system with a BIOS that supports booting from NVMe-oF over TCP. Contact your hardware vendor for information about support for this feature. Booting from NVMe-oF over TCP is currently only supported on UEFI platforms.

17.5.2 Installation #

To install SLES from NVMe-oF over TCP, proceed as follows:

Use the host system's UEFI setup menus to configure NVMe-oF connections to be established at boot time. Typically, you need to configure both networking (local IP addresses, gateways, etc.) and NVMe-oF targets (remote IP address, subsystem NQN or discovery NQN). Refer to the hardware documentaion for the configuration description. Your hardware vendor may provide means to manage the BIOS configuration centrally and remotely. Please contact your hardware vendor for additional information.
Prepare the installation as described in Deployment Guide.
Start the system installation using any supported installation method. You do not need to use any specific boot parameters to enable installation on NVMe-oF over TCP.
If the BIOS has been configured correctly, the disk partitioning dialog in YaST will show NVMe namespaces exported by the subsystems configured in the BIOS. They will be displayed as NVMe devices, where the tcp string indicates that the devices are connected via the TCP transport. Install the operating system (in particular the EFI boot partition and the root file system) on these namespaces.
Complete the installation.

After installation, the system should boot from NVMe-oF over TCP automatically. If it does not, check if the boot priority is set correctly in the BIOS setup.

The network interfaces used for booting are named nbft0, nbft1 and so on. To get information about the NVMe-oF boot, run the command:

# nvme nbft show

17.6 More information #

For more details about the abilities of the nvme command, refer to nvme nvme-help.

The following links provide a basic introduction to NVMe and NVMe-oF:

17 NVMe-oF #