===== What's this? =====
  * I bought an external enclosures, connected via USB3, to run NVMe
  * enclosure 1 details:
    * https://www.amazon.co.jp/gp/product/B07YTT4FJH
    * ELUTENG Type C M.2 SSD enclosure NVME USB3.1 Gen2 10Gbps
    * lsusb: ID 174c:2362 ASMedia Technology Inc. Best USB Device
    * can do TRIM, with extra udev rule
  * enclosure 2 details:
    * disappeared from Amazon-Japan
    * lsusb: ID 0bda:9210Realtek Semiconductor Corp. RTL9210 M.2 NVME Adapter
    * can do TRIM, with extra udev rule

===== Udev rule to perform TRIM =====
Mounting the device per default, no TRIM is supported:
<code>
fstrim: /mnt/tmp: the discard operation is not supported
</code>
Setting up a special udev rule:
<code>
# cat >/etc/udev/rules.d/10-extern-nvme.rules <<EOT
ACTION=="add", SUBSYSTEM=="scsi_disk", SUBSYSTEMS=="usb", ATTRS{idVendor}=="174c", ATTRS{idProduct}=="2362", ATTR{provisioning_mode}="unmap"
ACTION=="add", SUBSYSTEM=="scsi_disk", SUBSYSTEMS=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="9210", ATTR{provisioning_mode}="unmap"
EOT
# udevadm trigger
</code>
Then unplug/plug the device, and after mounting 'fstrim' succeeds.

===== Performance impact intern vs. extern NVMe =====
Running the 256GB SSD internally in a Thinkpad L480, measuring uncached reads blockwise:
<code>
# dd if=/dev/nvme0n1 of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.771196 s, 1.4 GB/s
</code>
Connecting the same drive externally via the enclosure:
<code>
# dd if=/dev/sda of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.42096 s, 444 MB/s
</code>