Configuring filesystem “TRIM” options on Fedora or RHEL

The SATA TRIM option, or discard if you use enterprise SCSI/SAS, that everyone likes to ensure their whiz bang SSD supports actually needs some configuration on Linux. There’s a few tasks that need to be done and some depend on your partitioning configuration.

Filesystem mount options: You’ll need to be using ext4/xfs/btrfs and mount with the “-o discard” option. To do this automatically in /etc/fstab just add ,discard after the defaults option.

LVM config: In /etc/lvm/lvm.conf file set the issue_discards option to 1. So issue_discards = 1.

LUKS config: In /etc/crypttab file add discards to the end of the appropriate luks lines, likely it’ll look like the following: none discards. It’s worth nothing there are some security implications by enabling discards with an encrypted filesystem.

For the fstab changes to take effect you just need to reboot. For the LVM and crypttab changes to take effect you also need to regenerate the initrd (or just wait for the next kernel update 🙂 ).

The above will enable online discards. You can also do it in batches with the fstrim command which is as simple as fstrim mount-point.