 Since version 3.7 of the Linux kernel mainline, md supports TRIM operations for the underlying solid-state drives (SSDs), for linear, RAID 0, RAID 1, RAID 5 and RAID 10 layouts.Since support for MD is found in the kernel, there is an issue with using it before the kernel is running.Specifically it "will not" be present if the boot loader is either (e)LiLo or GRUB legacy.