It's a matter of user space tools preference. Both mdadm, and lvm tools use the Linux md driver code to implement RAID on the backend; but have completely different user facing tools and on-disk metadata. So it's best to be familiar with the troubleshooting and recovery process for each more than create, because that's where people get into trouble the most with both sets of tools. This thread might help: https://www.centos.org/forums/viewtopic.php?f=47&t=51349 -- Chris Murphy