$ sudo pvcreate /dev/nvme0n1 Physical volume "/dev/nvme0n1" successfully created. $ sudo pvcreate /dev/sdb Physical volume "/dev/sdb" successfully created. $ sudo vgcreate vg-cache /dev/nvme0n1 /dev/sdb Volume group "vg-cache" successfully created $ sudo lvcreate -n slow -l90%FREE vg-cache /dev/sdb Logical volume "slow" created. $ sudo lvcreate -n fast -L 10G vg-cache /dev/nvme0n1 $ sudo modprobe dm-writecache $ sudo lvchange -a n vg-cache/fast $ sudo lvchange -a n vg-cache/slow $ sudo lvconvert --type writecache --cachevol fast vg-cache/slow $ sudo lvchange -a y vg-cache/slow $ sudo lvconvert --splitcache vg-cache/slow $ sudo blockdev --getsz /dev/vg-cache/slow 12744687616 $ sudo dmsetup create wc --table "0 78151680 writecache s /dev/vg-cache/slow /dev/vg-cache/fast 4096 0" $ sudo dmsetup message /dev/mapper/wc 0 flush $ dmsetup remove /dev/mapper/wc