## Recommended equipment

#### Brand: UGREEN

- **Port:** USB 3.0 2.5-Inch SATA

- **Mode/PID:** CM237
 
- **Main Controller:** ***ASM1153E***

    (Very important, not all drive support UAS, this Model CM237 has tested that was supported.)

- **Support:** UAS Transfer Protocol

----

## OPEN Trim for external USB SSD

#### 1. Check TRIM support

```
sudo fstrim -v /
```

**fstrim: /run/media/telgar/ssd: the discard operation is not supported**

```
$ lsblk --discard /dev/sda
NAME   DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO
sdb           0        0B       0B         0
├─sda1        0        0B       0B         0
└─sda2        0        0B       0B         0
```

If the **DISC-MAX** value is **0B**, then TRIM is not **enabled**.

#### 2. Enable TRIM

Find the USB **idVendor** and **idProduct** :

```
$ lsusb
...
Bus 002 Device 002: ID 174c:1153 ASMedia Technology Inc. ASM1153 SATA 3Gb/s bridge
...
```

Add **/etc/udev/rules.d/50-usb-ssd-trim.rules**

```
ACTION=="add|change", ATTRS{idVendor}=="174c", ATTRS{idProduct}=="1153", SUBSYSTEM=="scsi_disk", ATTR{provisioning_mode}="unmap"
```

Then reboot, the TRIM will be **enabled**.

#### 3.Fstrim the SSD device

1'st time, run "**fstrim -v /**" successfully:

```
$ sudo fstrim -v /
/: 111.4 GiB (119574462464 bytes) trimmed
```

```
$ lsblk --discard /dev/sdb
NAME   DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO
sda           0      512B       4G         0
├─sda1        0      512B       4G         0
└─sda2        0      512B       4G         0
```

#### 4.Automatic trimming

The last thing you will need to do to make sure the TRIM command is run automatically in the background 

(so you don't need to run fstrim manually) is to enable the built-in fstrim.timer.

To do that, run the command:

```
$ sudo systemctl enable fstrim.timer
```

By default, it will run weekly.

----

All done.