Back up your system.
Identify the disk media name for the disk you intend to remove.
# vxdisk list | grep cwtxdysz
For example, if the disk to be removed is c2t1d0, enter:
# vxdisk list | grep c2t1d0 c2t1d0s2 sliced disk01 rootdg online
The disk media name is the third field in the output above: disk01.
You can use the vxdiskadm utility to prepare the disk for removal.
Type vxdiskadm in a shell.
This operation is interactive and requires user confirmation of the operation.
Select the "Remove a disk" option.
When prompted for a disk name to remove, type the disk media name from Step 2.
vxdiskadm marks the disk to be removed.
Refer to the vxdiskadm(1M) man page for further details.