Chapter 10. Freeing space on thinly-provisioned logical volumes using fstrim

You can manually run fstrim to return unused logical volume space to the thin pool so that it is available for other logical volumes.

Red Hat recommends running fstrim daily.

Prerequisites

Verify that the thin pool logical volume supports discard behavior.
Discard is supported if the output of the following command for the underlying device is not zero.
```
# cat /sys/block/<device>/queue/discard_max_bytes
```

Procedure

Run fstrim to restore physical space to the thin pool.
```
# fstrim -v <mountpoint>
```
For example, the following command discards any unused space it finds on the logical volume mounted at /gluster_bricks/data/data, and provides verbose output (-v).
```
# fstrim -v /gluster_bricks/data/data
```

Additional resources

See Scheduling a recurring job using cron for information on configuring an automatically recurring task.

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