Similar idea of fstrim, use SSD as backend of Lustre filesystem might have performances
drop with gc running in the background.

We have mount option '-o discard'(etc) for ldiskfs to trigger discard automatically
whenever filesystem free some space, but as our benchmarking this could
introduce latency too, and also this is somehow out of control.

So it is desirable for administrators to do trim manually, for example
doing trim if system are idle.