I’ve found several manuals describing how to add second disk to Volume Group and transform it into mirror. This does not looks complex, and everyone can do it, when everything is working like described in documentation. The problems start when something goes wrong, and one of steps failed.
In my environment there is virtual machine with CentOS 7 hosted by VMWare ESXi. This VM has system disk on one datastore. To provide redundation on OS level I decided to add second disk with the same capacity from another datastore and create RAID-1 (mirror) on them.
Migration root disk into mirror in LVM
