@lamp using a #RAID without #dmraid only works well with things like #RAID1 on a boot partition since that's the only way to keeo it sync and be bootable...

I usually choose to make lvm partitions to do dmraid and also choose to keep at least 25% vacant for #WearLeveling and #GarbageCollection as well as #TRIM to work, and round it down so I can mix & match drives

But then again going #ZFS is the smarter route...