The format(1M) command recognizes all virtual disks that are present in a domain. However, for virtual disks that are exported as single-slice disks, the format command cannot change the partition table of the virtual disk. Commands such as label will fail unless you try to write a disk label similar to the one that is already associated with the virtual disk.
Virtual disks whose backends are SCSI disks support all format(1M) subcommands. Virtual disks whose backends are not SCSI disks do not support some format(1M) subcommands, such as repair and defect. In that case, the behavior of format(1M) is similar to the behavior of Integrated Drive Electronics (IDE) disks.