Hello, I have create a software raid level 1 with mdadm. One drive is a "classic" HDD. The 2'nd drive is a SSD with option "write-mostly". Over the raid I have create and LVM with all the partitions (root,swap and qemu/KVM VM's). When I understand mdadm the hole space is marked as used. So my question is how useful is fstrim on /dev/mdx and would it relay trim the SSD? Best Regards,