By specifying a disk as "keep" type and registering it with root class, you can retain the disk data while configuring mirroring. However, you cannot register the disk under the following conditions. In such case, change the disk configuration and try registering again.
The disk's slice numbers are all in use. In other words, the number of slices created on the disk has reached the upper limit (seven).
There is not sufficient free space area or swap area on the disk for private slice.
For details on free space area (or swap area), see "A.2.7 Disk Size."
Additionally, when registering physical disks other than system disks (with running /, /usr, /var, 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.
