By specifying a disk as "keep" type and registering it with root class, you can retain the disk data while configuring mirroring. The disk to be registered with root class as a keep disk must conform to the following conditions:
The disk label is the GPT type.
The number of slices is 14 or less.
The system disk has sufficient free space.
For details on free space area, see "2.3.9 Disk Size."
Additionally, when registering physical disks other than system disks (with running /, /usr, /var, /boot, /boot/efi, or swap areas) as keep disks, all slices on the physical disks must be in open status. For example, if the slice is mounted as a file system, unmount it in advance.
You cannot register a keep disk with local class or shared class.
