This message was deleted.

That's normal, I'd guess. You could use the "discard" mount option (if using XFS?), but an

fstrim

prior to the backup run would be a good idea. LH itself can't tell whether the blocks are free'd unless the file system tells us about them.

Thank you - that helped me find some pointers - I will run some test with the discard mount option - are there any risks that you know of that I should be aware of in doing this?

It says to have some significant performance impact, but for LH on flash, maybe that's not actually relevant and I suspect your testing would show that quickly. Calling fstrim only before the backup might be slightly more efficient, but it's worth trying. Please share your results!