Few months ago I installed Fedora 19 on my new laptop with Samsung SSD and yesterday I found out TRIM is not enabled by default. I was installing using standard options with LVM/LUKS/ext4 partitions.
There were some problems in Fedora 18 with LUKS not propagating TRIM commands, but this was fixed in Fedora 19. On my system, TRIM commands propagate successfully. One just needs to make few changes in the configuration. First of all, we need to check if TRIM propagates for all partitions to the end device:
[lzap@lzapx ~]$ lsblk -D NAME DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO sda 0 512B 2G 1 ├─sda1 0 512B 2G 1 └─sda2 0 512B 2G 1 ├─fedora_lzapx-root 0 512B 2G 1 ├─fedora_lzapx-swap 0 512B 2G 1 └─fedora_lzapx-home 0 512B 2G 1 └─luks-aaaaaaaa-6657-44f4-8297-bbbbbbbb1111 0 512B 2G 0
The last column shows if TRIM commands do propagate. We can see all is set, except the encrypted home (the last line). To get full TRIM support on LUKS-encrypted devices, we need to allow TRIM commands. Note that this can decrease encryption strengh. This is the Fedora 19 default crypttab file:
$ cat /etc/crypttab luks-aaaaaaaa-6657-44f4-8297-bbbbbbbb1111 UUID=aaaaaaaa-6657-44f4-8297-a571e02e5492 none
discard (used to be
allow-discards in older versions of Fedora - updated) option there:
$ cat /etc/crypttab luks-aaaaaaaa-6657-44f4-8297-bbbbbbbb1111 UUID=aaaaaaaa-6657-44f4-8297-a571e02e5492 none discard
After reboot, LUKS can be checked (for discards flag) with:
[lzap@lzapx ~]$ sudo cryptsetup status luks-aaaaaaaa-6657-44f4-8297-bbbbbbbb1111 /dev/mapper/luks-aaaaaaaa-6657-44f4-8297-bbbbbbbb1111 is active and is in use. type: LUKS1 cipher: aes-xts-plain64 keysize: 512 bits device: /dev/mapper/fedora_lzapx-home offset: 4096 sectors size: 370683904 sectors mode: read/write flags: discards
lsblk command will still show zero for the LUKS partition (this is
normal). You should have the whole chain with
should give you
Before we get to the actual configuration, there are two optional steps you can do.
Optional LVM configuration
If you modify your LVM logical volumes often (e.g. shrinking, deleting), you
want to set issue_discards to 1 in
/etc/lvm/lvm.conf. Then you need to do
the next optional step described bellow.
Optional init RAM disk regeneration
If you have root partition encrypted by LUKS (not my case) or if you have your root partition on LVM and you want LVM trimming when shrinking or deleting (see above optional step), initial RAM disk needs to be regenerated using the following command:
You will need to reboot to make this change effective of course.
Now, to enable TRIM and take advantage of it, there are two options:
TRIM when deleting files
It is possible to configure ext4 to send TRIM commands while deleting data.
You can do this by adding
discard option to partitions in
that this slows down deleting a bit. It depends on the SSD drive, but this can
slow down quite significantly on some drives.
Do not put
discard option to swap devices as this is not required (and
perhaps it will not work either). Swap is SSD friendly by default and
propagates TRIM command.
TRIM via systemd service
Preferred option for those who do not want to play around with anything and want to discard later (when computer is at idle). To enable this option, do this:
systemctl enable fstrim.timer systemctl start fstrim.timer
This timer was not enabled on my system by default, but I am upgrading my Fedora twice an year and I can’t tell if this is the same for new installations.
TRIM from cron
This is my preferred option because it can be scheduled daily, weekly or during night if you do not turn off your laptop/server:
cat /etc/cron.weekly/01-fstrim #!/bin/sh fstrim / fstrim /home chmod +x /etc/cron.weekly/01-fstrim
Try to run the script now, it should not print any error message. If you changed LUKS configuration, you might need restart before doing that. If you delete lots of files often, consider scheduling trimming every day or even every hour. The more you trim, the faster the process should be.
That’s all folks. I would like to thank Lukáš Czerner, Kamil Páral and Chris Smart for helping me with this.