CONFIG_NVME_TCP=m
CONFIG_NVME_TARGET_TCP=m

$ sudo blockdev --getsize64 /dev/sdb
7000259821568

$ for i in sdb sdc sdd sde; do sudo parted --script /dev/$i mklabel gpt mkpart primary 1MB 100%; done

$ sudo blockdev --getsize64 /dev/sdb1
7000257724416


sudo blockdev --getsize64 /dev/nvme0n1
250059350016

$ sudo parted --script /dev/nvme0n1 mklabel gpt mkpart primary 1MB 100%
$ cat /proc/partitions | grep nvme
 259        0  244198584 nvme0n1
 259        2  244197376 nvme0n1p1
 
$ sudo mdadm --create /dev/md0 --level=5 --raid-devices=4 --write-journal=/dev/nvme0n1p1 --bitmap=none /dev/sdb1 /dev/sdc1/dev/sdd1 /dev/sde1
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.


$ cat /proc/partitions | grep md
   9        0 20508171264 md0


$ sudo blockdev --getsize64 /dev/md0
21000367374336

$ echo "write-back" | sudo tee /sys/block/md0/md/journal_mode > /dev/null
$ cat /sys/block/md0/md/journal_mode
write-through [write-back]

$ git clone https://github.com/pkoutoupis/rapiddisk.git
$ cd rapiddisk/
$ make
$ sudo make install
$ sudo modprobe rapiddisk
$ sudo modprobe rapiddisk-cache

$ sudo rapiddisk --attach 2048
rapiddisk 6.0
Copyright 2011 - 2019 Petros Koutoupis
   
Attached device rd0 of size 2048 Mbytes

$ sudo rapiddisk --cache-map rd0 /dev/md0 wa
rapiddisk 6.0
Copyright 2011 - 2019 Petros Koutoupis
   
Command to map rc-wa_md0 with rd0 and /dev/md0 has been sent.
Verify with "--list"

$ ls -l /dev/mapper/rc-wa_md0
brw------- 1 root root 253, 0 Jan 16 23:15 /dev/mapper/rc-wa_md0

$ sudo modprobe nvmet
$ sudo modprobe nvmet-tcp

$ sudo /bin/mount -t configfs none /sys/kernel/config/
$ mount | grep configfs
configfs on /sys/kernel/config type configfs (rw,relatime)

$ sudo mkdir /sys/kernel/config/nvmet/subsystems/nvmet-test
$ cd /sys/kernel/config/nvmet/subsystems/nvmet-test

$ echo 1 | sudo tee -a attr_allow_any_host > /dev/null

$ sudo mkdir namespaces/1
$ cd namespaces/1/

$ echo -n /dev/mapper/rc-wa_md0 | sudo tee -a device_path > /dev/null
$ echo 1 | sudo tee -a enable > /dev/null

$ sudo mkdir /sys/kernel/config/nvmet/ports/1
$ cd /sys/kernel/config/nvmet/ports/1

$ echo 10.0.0.185 | sudo tee -a addr_traddr > /dev/null
$ echo tcp | sudo tee -a addr_trtype > /dev/null
$ echo 4420 | sudo tee -a addr_trsvcid > /dev/null
$ echo ipv4 | sudo tee -a addr_adrfam > /dev/null

$ sudo ln -s /sys/kernel/config/nvmet/subsystems/nvmet-test/ /sys/kernel/config/nvmet/ports/1/subsystems/nvmet-test
$ dmesg | grep "nvmet_tcp"
[ 9360.176859] nvmet_tcp: enabling port 1 (10.0.0.185:4420)

$ modprobe nvme
$ modprobe nvme-tcp

$ sudo nvme connect -t tcp -n nvmet-test -a 10.0.0.185 -s 4420

$ cat /proc/partitions | grep nvme
 259        0 20508171264 nvme0n1