Chapter 4. Trim options on an LVM-VDO volume
You can mount your file system with the discard option, which informs the VDO volume of the unused space. Another option is to use the fstrim application, which is an on-demand discarding, or mount -o discard command for immediate discarding.
When using the fstrim application, the admin needs to schedule and monitor an additional process, while using mount -o discard command allows for immediate recovery of space when possible.
Note that it is currently recommended to use fstrim application to discard unused blocks rather than the discard mount option because the performance impact of this option can be quite severe. For this reason, nodiscard is the default.
4.1. Enabling discard mount option on VDO
This procedure enables the discard option on your VDO volume.
Prerequisites
- An LVM-VDO volume exists on your system.
Procedure
Enable the
discardon your volume:# mount -o discard /dev/vg-name/vdo-name mount-point
Additional resources
-
xfs(5),mount(8), andlvmvdo(7)man pages
4.2. Setting up periodic TRIM operation
This procedure enables a scheduled TRIM operation on your system.
Prerequisites
- An LVM-VDO volume exists on your system.
Procedure
Enable and start the timer:
# systemctl enable --now fstrim.timer
Verification
Verify that the timer is enabled:
# systemctl list-timers fstrim.timer
Example 4.1. Possible output of the verification procedure
# systemctl list-timers fstrim.timer NEXT LEFT LAST PASSED UNIT ACTIVATES Mon 2021-05-10 00:00:00 EDT 5 days left n/a n/a fstrim.timer fstrim.service
You will not see any reference to a VDO volume, because the fstrim.timer runs across all mounted filesystems.
Additional resources
-
fstrim(8)man page
