Check disk size belong to vg , take two same size disk to mirror

# bootinfo -s hdisk2

#lsvg -p rootvg

Add one more disk of same size of already have disk having rootvg.

# extendvg rootvg hdisk2

# lsvg -p rootvg

Now mirror vg with background sync LV. It sync LVs in background with new LVs

# mirrorvg -s rootvg

Create a boot image

# bosboot -ad /dev/hdisk2

#bosboot -ad /dev/hdisk1

Add a blv

record of newly added disk, first check and then add.

# bootlist -m normal -o

#bootlist -m normal hdisk2 hdisk1