NVMe

NVM Express

Links

• nvmexpress.org
• arch linux nvme doc
• How to Deploy High-Performance Multi-Tenant Object Storage with NVMe
• NVMe-oF Host Configuration for SUSE Linux Enterprise Server 15 SP3 with ONTAP

NVMe/TCP

• https://www.networkworld.com/article/3609921/nvme-over-tcp-how-it-supercharges-ssd-storage-using-standard-ip-networks.html
• nvme and tcp
• NVMe over TCP
• https://tekdeeps.com/what-is-nvme-over-tcp-how-to-use/
• Data in a Flash, Part III: NVMe over Fabrics Using TCP
• nvme-tcp storage operations

Qemu and NVMe

• Qemu and nvme

Hardware

Slots

M.2

The old way, on standard motherboards.

https://arstechnica.com/gadgets/2015/02/understanding-m-2-the-interface-that-will-speed-up-your-next-ssd/

U.2

• https://www.drewthorst.com/posts/nvme/namespaces/readme/

Hotplug

• https://en.wikipedia.org/wiki/U.2

Tools

nvmetcli

NVMe target admin tool

https://github.com/JunxiongGuan/nvmetcli

Documentation

NVMe device names

• NVME device names

Example: /dev/nvme0n2p3

Means nvme device 0, namespace 2, partition 3 The first namespace, n1, will always exist

NVMe multipathing

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_storage_devices/enabling-multipathing-on-nvme-devices_managing-storage-devices

Namespaces

MNAM: Maximum Number of Allowed Namespaces

• nvme namespaces
• Drew Thorstensen - NVME namespaces
• https://narasimhan-v.github.io/2020/06/12/Managing-NVMe-Namespaces.html

HOWTO

On NVMe target

Deleting an nvme target

NAME=nvmetest
PORT=1
NODENUM=1
cd /sys/kernel/config/nvmet
rm -rf ports/1/subsystems/$NAME
rmdir ports/$PORT
rmdir subsystems/$NAME-$NODENUM/namespaces/$PORT/
rmdir subsystems/$NAME-$NODENUM/

List devices

nvme list

get details

nvme id-ctrl /dev/nvme0

if you want to find for example IP and NQN of a device:

nvme list-subsys /dev/nvme2n1

of just

nvme list-subsys

Show subnqn of device

nvme id-ctrl /dev/nvme1n2 | grep subnqn

Namespaces

Difference between size and capacity

nsze vs ncap flbas = blocksize

To check them in a namespace:

nvme id-ns /dev/nvme1n3 | egrep "nsze|ncap|flbas"

Get block size:

nvme id-ns /dev/nvme1n3 | grep "in use"

which gives like

lbaf  1 : ms:0   lbads:12 rp:0 (in use)

where lbads is the blocksize in 2^lbads, so in this case 2^12 = 4096

Create namespace

• Managing NVMe namespaces

Get controller id

nvme id-ctrl /dev/nvme1 | grep cntlid

gives like

cntlid    : 0x1

Create 100G namespace, -s (--nsze) and -c (--ncap) is number of blocks -b, --blocksize

nvme create-ns /dev/nvme1 -s 26214387 -c 26214387 -b 4096

TODO: what about --flbas instead of blocksize?

To actually use the namespace you need to to attach it first

nvme attach-ns /dev/nvme1 

List namespaces

nvme list-ns /dev/nvme1

Show info about namespace

nvme id-ns /dev/nvme1n1

Show number of available namespaces

nvme id-ctrl /dev/nvme1|grep nn

Show total capacity

nvme id-ctrl /dev/nvme1|grep tnvmcap

Show unallocated capacity

nvme id-ctrl /dev/nvme1|grep unvmcap

NVMe over fabrics

https://www.linuxjournal.com/content/data-flash-part-iii-nvme-over-fabrics-using-tcp

You might want to use nvmetcli on the target:

https://github.com/JunxiongGuan/nvmetcli

Dependencies: python3-configshell-fb

NVMe-oF target

/bin/mount -t configfs none /sys/kernel/config/

Show active targets

?

NVMe/TCP Host

In this context Host means client/initiator

See Configuring an NVMe/TCP host

Client

Modules:

nvme_rdma nvme_core nvme_fabrics and more

Connect on boot

Check /etc/nvme/discovery.conf

systemctl enable nvmf-autoconnect.service

Show remote connections

nvme list-subsys

Monitoring nvme

• Monitoring nvme with zabbix

Terms and acronyms

flbas

Formatted LBA Sizes

FAQ

Errors on client/host

Failed to open /dev/nvme-fabrics: No such file or directory

modprobe nvme-tcp

or maybe rdma

Failed to write to /dev/nvme-fabrics: Connection refused

dmesg will probably show

nvme0: failed to connect socket: -111

Maybe you're using something like infiniband, try

nvme discover -t rdma ...

Failed to write to /dev/nvme-fabrics: Input/output error

Mayve you're trying to connect to a nonexisting nqn

Failed to write to /dev/nvme-fabrics: Invalid argument

Check dmesg

nvme nvme0: Invalid MNAN value 1024

Try

modprobe nvme_core multipath=N

(remember to rmmod first :)

nvme_fabrics: no handler found for transport drma.

Check your /etc/nvme/discover.conf, it should be rdma :)

nvmet_tcp: malformed ip/port passed: :4420

Maybe forgot to set addr_traddr ?

Duplicate cntlid 1 with nvme0

Make sure next connection is on new control id, /dev/nvme0x vs /dev/nvme1x TODO ??

IDs don't match for shared namespace 1

??