# Solid State Drives

Post installation, you will need to enable TRIM for solid state drives. You can
check which devices allow TRIM by running:

```
$ lsblk --discard
```

If the DISC-GRAN (discard granularity) and DISC-MAX (discard maximum bytes)
columns are non-zero, that means the block device has TRIM support. If your
solid state drive partition does not show TRIM support, please verify that you
chose a file system with TRIM support (ext4, Btrfs, F2FS, etc.). Note that F2FS
requires kernel 4.19 or above to support TRIM.

To run TRIM one-shot, you can run
[`fstrim(8)`](https://man.voidlinux.org/fstrim.8) manually. For example, if your
/ directory is on an SSD:

```
# fstrim /
```

To automate running TRIM, use cron or add the `discard` option to `/etc/fstab`.

## Periodic TRIM with cron

Add the following lines to `/etc/cron.weekly/fstrim`:

```
#!/bin/sh

fstrim /
```

Finally, make the script executable:

```
# chmod u+x /etc/cron.weekly/fstrim
```

## Continuous TRIM with fstab discard

You can use either continuous or periodic TRIM, but usage of continuous TRIM is
discouraged if you have an SSD that doesn't handle NCQ correctly. Refer to the
kernel
[blacklist](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/ata/libata-core.c?h=v5.8&id=bcf876870b95592b52519ed4aafcf9d95999bc9c#n3774).

Edit `/etc/fstab` and add the `discard` option to block devices that need TRIM.

For example, if `/dev/sda1` was an SSD partition, formatted as ext4, and mounted
at `/`:

```
/dev/sda1  /           ext4  defaults,discard   0  1
```

## LVM

To enable TRIM for LVM's commands (`lvremove`, `lvreduce`, etc.), open
`/etc/lvm/lvm.conf`, uncomment the `issue_discards` option, and set it to `1`:

```
issue_discards=1
```

## LUKS

**Warning**: Before enabling discard for your LUKS partition, please be aware of
the [security
implications](https://wiki.archlinux.org/index.php/Dm-crypt/Specialties#Discard/TRIM_support_for_solid_state_drives_(SSD)).

To open an encrypted LUKS device and allow discards to pass through, open the
device with the `--allow-discards` option:

```
# cryptsetup luksOpen --allow-discards /dev/sdaX luks
```

### Non-root devices

Edit `/etc/crypttab` and set the `discard` option for devices on the SSD. For
example, if you have a LUKS device with the name `externaldrive1`, device
`/dev/sdb2`, and password `none`:

```
externaldrive1  /dev/sdb2   none    luks,discard
```

### Root devices

If your root device is on LUKS, add `rd.luks.allow-discards` to
`CMDLINE_LINUX_DEFAULT`. In the case of GRUB, edit `/etc/default/grub`:

```
GRUB_CMDLINE_LINUX_DEFAULT="rd.luks.allow-discards"
```

### Verifying configuration

To verify that you have configured TRIM correctly for LUKS, run:

```
# dmsetup table /dev/mapper/crypt_dev --showkeys
```

If this command output contains the string `allow_discards`, you have
successfully enabled TRIM on your LUKS device.

## ZFS

Before running `trim` on a ZFS pool, ensure that all devices in the pool support
it:

```
# zpool get all | grep trim
```

If the pool allows `autotrim` (set `off` by default), you can `trim` the pool
periodically or automatically. To one-shot `trim` `yourpoolname`:

```
# zpool trim yourpoolname
```

### Periodic TRIM

Add the following lines to `/etc/cron.daily/ztrim`:

```
#!/bin/sh
zpool trim yourpoolname
```

Finally, make the script executable:

```
# chmod u+x /etc/cron.daily/ztrim
```

### Autotrim

To set autotrim for `yourpoolname`, run:

```
# zpool set autotrim=on yourpoolname
```